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	$85.35	7.194%	$91.4901	$91.49	$91.50	$91.50
Purchase #2	$190.65	3.282%	$196.9071	$196.91	$196.90	$196.90
Purchase #3	$153.26	9.507%	$167.8304	$167.83	$167.85	$167.80
Purchase #4	$37.40	4.420%	$39.0531	$39.05	$39.05	$39.10
Purchase #5	$191.53	4.333%	$199.829	$199.83	$199.85	$199.80
Purchase #6	$202.30	10.394%	$223.3271	$223.33	$223.35	$223.30
Purchase #7	$120.26	13.118%	$136.0357	$136.04	$136.05	$136.00
7 purchase totals =	$980.75		$1,054.4725	$1,054.48	$1,054.55	$1,054.40