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	$42.40	5.522%	$44.7413	$44.74	$44.75	$44.70
Purchase #2	$246.70	11.693%	$275.5466	$275.55	$275.55	$275.50
Purchase #3	$61.64	4.861%	$64.6363	$64.64	$64.65	$64.60
Purchase #4	$96.25	3.489%	$99.6082	$99.61	$99.60	$99.60
Purchase #5	$53.90	13.749%	$61.3107	$61.31	$61.30	$61.30
Purchase #6	$211.40	5.780%	$223.6189	$223.62	$223.60	$223.60
Purchase #7	$250.99	13.719%	$285.4233	$285.42	$285.40	$285.40
7 purchase totals =	$963.28		$1,054.8853	$1,054.89	$1,054.85	$1,054.70