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	$31.73	6.533%	$33.8029	$33.80	$33.80	$33.80
Purchase #2	$73.29	5.536%	$77.3473	$77.35	$77.35	$77.30
Purchase #3	$233.67	6.224%	$248.2136	$248.21	$248.20	$248.20
Purchase #4	$115.51	10.510%	$127.6501	$127.65	$127.65	$127.70
Purchase #5	$154.56	8.299%	$167.3869	$167.39	$167.40	$167.40
Purchase #6	$103.83	5.242%	$109.2728	$109.27	$109.25	$109.30
Purchase #7	$160.30	4.740%	$167.8982	$167.90	$167.90	$167.90
7 purchase totals =	$872.89		$931.5718	$931.57	$931.55	$931.60