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	$79.33	10.807%	$87.9032	$87.90	$87.90	$87.90
Purchase #2	$165.26	11.862%	$184.8631	$184.86	$184.85	$184.90
Purchase #3	$104.59	6.556%	$111.4469	$111.45	$111.45	$111.40
Purchase #4	$166.93	7.435%	$179.3412	$179.34	$179.35	$179.30
Purchase #5	$156.34	6.726%	$166.8554	$166.86	$166.85	$166.90
Purchase #6	$100.46	11.397%	$111.9094	$111.91	$111.90	$111.90
Purchase #7	$191.75	11.140%	$213.111	$213.11	$213.10	$213.10
7 purchase totals =	$964.66		$1,055.4302	$1,055.43	$1,055.40	$1,055.40