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	$88.34	9.276%	$96.5344	$96.53	$96.55	$96.50
Purchase #2	$67.41	5.783%	$71.3083	$71.31	$71.30	$71.30
Purchase #3	$69.60	13.143%	$78.7475	$78.75	$78.75	$78.70
Purchase #4	$228.44	9.400%	$249.9134	$249.91	$249.90	$249.90
Purchase #5	$30.67	4.775%	$32.1345	$32.13	$32.15	$32.10
Purchase #6	$81.67	5.809%	$86.4142	$86.41	$86.40	$86.40
Purchase #7	$93.65	7.640%	$100.8049	$100.80	$100.80	$100.80
7 purchase totals =	$659.78		$715.8572	$715.84	$715.85	$715.70