Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$182.33	13.451%	$206.8552	$206.86	$206.85	$206.90
Purchase #2	$157.55	6.192%	$167.3055	$167.31	$167.30	$167.30
Purchase #3	$110.50	4.639%	$115.6261	$115.63	$115.65	$115.60
Purchase #4	$179.64	11.793%	$200.8249	$200.82	$200.80	$200.80
Purchase #5	$211.49	4.721%	$221.4744	$221.47	$221.45	$221.50
Purchase #6	$111.89	11.443%	$124.6936	$124.69	$124.70	$124.70
Purchase #7	$109.32	8.233%	$118.3203	$118.32	$118.30	$118.30
7 purchase totals =	$1,062.72		$1,155.1000	$1,155.10	$1,155.05	$1,155.10