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	$93.40	12.672%	$105.2356	$105.24	$105.25	$105.20
Purchase #2	$167.91	12.795%	$189.3941	$189.39	$189.40	$189.40
Purchase #3	$134.66	5.759%	$142.4151	$142.42	$142.40	$142.40
Purchase #4	$68.72	3.631%	$71.2152	$71.22	$71.20	$71.20
Purchase #5	$222.65	7.444%	$239.2241	$239.22	$239.20	$239.20
Purchase #6	$43.36	4.481%	$45.303	$45.30	$45.30	$45.30
Purchase #7	$157.27	6.666%	$167.7536	$167.75	$167.75	$167.80
7 purchase totals =	$887.97		$960.5407	$960.54	$960.50	$960.50