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	$128.93	9.731%	$141.4762	$141.48	$141.50	$141.50
Purchase #2	$74.54	5.268%	$78.4668	$78.47	$78.45	$78.50
Purchase #3	$196.25	8.224%	$212.3896	$212.39	$212.40	$212.40
Purchase #4	$167.58	10.427%	$185.0536	$185.05	$185.05	$185.10
Purchase #5	$142.68	13.631%	$162.1287	$162.13	$162.15	$162.10
Purchase #6	$81.77	8.279%	$88.5397	$88.54	$88.55	$88.50
Purchase #7	$161.63	10.258%	$178.21	$178.21	$178.20	$178.20
7 purchase totals =	$953.38		$1,046.2646	$1,046.27	$1,046.30	$1,046.30