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	$202.29	10.488%	$223.5062	$223.51	$223.50	$223.50
Purchase #2	$55.61	10.873%	$61.6565	$61.66	$61.65	$61.70
Purchase #3	$220.94	4.836%	$231.6247	$231.62	$231.60	$231.60
Purchase #4	$194.33	3.463%	$201.0596	$201.06	$201.05	$201.10
Purchase #5	$147.91	13.796%	$168.3157	$168.32	$168.30	$168.30
Purchase #6	$127.52	4.624%	$133.4165	$133.42	$133.40	$133.40
Purchase #7	$105.92	3.212%	$109.3222	$109.32	$109.30	$109.30
7 purchase totals =	$1,054.52		$1,128.9014	$1,128.91	$1,128.80	$1,128.90