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	$107.82	3.469%	$111.5603	$111.56	$111.55	$111.60
Purchase #2	$221.96	10.852%	$246.0471	$246.05	$246.05	$246.00
Purchase #3	$136.96	11.446%	$152.6364	$152.64	$152.65	$152.60
Purchase #4	$65.39	9.149%	$71.3725	$71.37	$71.35	$71.40
Purchase #5	$206.35	6.108%	$218.9539	$218.95	$218.95	$219.00
Purchase #6	$128.39	6.301%	$136.4799	$136.48	$136.50	$136.50
Purchase #7	$108.33	5.764%	$114.5741	$114.57	$114.55	$114.60
7 purchase totals =	$975.20		$1,051.6242	$1,051.62	$1,051.60	$1,051.70