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	$104.99	12.623%	$118.2429	$118.24	$118.25	$118.20
Purchase #2	$133.65	6.842%	$142.7943	$142.79	$142.80	$142.80
Purchase #3	$100.35	11.330%	$111.7197	$111.72	$111.70	$111.70
Purchase #4	$246.77	12.212%	$276.9056	$276.91	$276.90	$276.90
Purchase #5	$75.33	4.281%	$78.5549	$78.55	$78.55	$78.60
Purchase #6	$184.27	10.441%	$203.5096	$203.51	$203.50	$203.50
Purchase #7	$199.73	4.813%	$209.343	$209.34	$209.35	$209.30
7 purchase totals =	$1,045.09		$1,141.0700	$1,141.06	$1,141.05	$1,141.00