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	$119.64	9.739%	$131.2917	$131.29	$131.30	$131.30
Purchase #2	$6.80	13.194%	$7.6972	$7.70	$7.70	$7.70
Purchase #3	$233.27	13.501%	$264.7638	$264.76	$264.75	$264.80
Purchase #4	$196.73	3.199%	$203.0234	$203.02	$203.00	$203.00
Purchase #5	$142.93	9.594%	$156.6427	$156.64	$156.65	$156.60
Purchase #6	$66.68	12.326%	$74.899	$74.90	$74.90	$74.90
Purchase #7	$236.26	10.688%	$261.5115	$261.51	$261.50	$261.50
7 purchase totals =	$1,002.31		$1,099.8293	$1,099.82	$1,099.80	$1,099.80