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	$80.61	12.672%	$90.8249	$90.82	$90.80	$90.80
Purchase #2	$150.27	11.278%	$167.2175	$167.22	$167.20	$167.20
Purchase #3	$247.34	13.812%	$281.5026	$281.50	$281.50	$281.50
Purchase #4	$239.88	10.283%	$264.5469	$264.55	$264.55	$264.50
Purchase #5	$115.80	9.751%	$127.0917	$127.09	$127.10	$127.10
Purchase #6	$56.40	7.510%	$60.6356	$60.64	$60.65	$60.60
Purchase #7	$18.57	11.444%	$20.6952	$20.70	$20.70	$20.70
7 purchase totals =	$908.87		$1,012.5144	$1,012.52	$1,012.50	$1,012.40