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	$67.41	5.779%	$71.3056	$71.31	$71.30	$71.30
Purchase #2	$70.89	13.745%	$80.6338	$80.63	$80.65	$80.60
Purchase #3	$212.59	12.300%	$238.7386	$238.74	$238.75	$238.70
Purchase #4	$79.52	12.511%	$89.4687	$89.47	$89.45	$89.50
Purchase #5	$234.74	9.830%	$257.8149	$257.81	$257.80	$257.80
Purchase #6	$190.99	8.309%	$206.8594	$206.86	$206.85	$206.90
Purchase #7	$176.73	11.531%	$197.1087	$197.11	$197.10	$197.10
7 purchase totals =	$1,032.87		$1,141.9297	$1,141.93	$1,141.90	$1,141.90