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	$90.45	3.173%	$93.32	$93.32	$93.30	$93.30
Purchase #2	$126.55	6.626%	$134.9352	$134.94	$134.95	$134.90
Purchase #3	$127.51	3.104%	$131.4679	$131.47	$131.45	$131.50
Purchase #4	$167.54	12.276%	$188.1072	$188.11	$188.10	$188.10
Purchase #5	$59.33	13.626%	$67.4143	$67.41	$67.40	$67.40
Purchase #6	$237.62	11.161%	$264.1408	$264.14	$264.15	$264.10
Purchase #7	$115.96	9.229%	$126.6619	$126.66	$126.65	$126.70
7 purchase totals =	$924.96		$1,006.0473	$1,006.05	$1,006.00	$1,006.00