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	$149.90	3.443%	$155.0611	$155.06	$155.05	$155.10
Purchase #2	$201.97	10.810%	$223.803	$223.80	$223.80	$223.80
Purchase #3	$235.86	12.293%	$264.8543	$264.85	$264.85	$264.90
Purchase #4	$67.55	6.608%	$72.0137	$72.01	$72.00	$72.00
Purchase #5	$36.46	13.349%	$41.327	$41.33	$41.35	$41.30
Purchase #6	$221.54	6.697%	$236.3765	$236.38	$236.40	$236.40
Purchase #7	$55.61	7.331%	$59.6868	$59.69	$59.70	$59.70
7 purchase totals =	$968.89		$1,053.1224	$1,053.12	$1,053.15	$1,053.20