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	$51.41	4.860%	$53.9085	$53.91	$53.90	$53.90
Purchase #2	$247.25	7.141%	$264.9061	$264.91	$264.90	$264.90
Purchase #3	$26.50	11.557%	$29.5626	$29.56	$29.55	$29.60
Purchase #4	$142.49	5.754%	$150.6889	$150.69	$150.70	$150.70
Purchase #5	$174.96	13.512%	$198.6006	$198.60	$198.60	$198.60
Purchase #6	$26.74	11.763%	$29.8854	$29.89	$29.90	$29.90
Purchase #7	$185.82	4.705%	$194.5628	$194.56	$194.55	$194.60
7 purchase totals =	$855.17		$922.1149	$922.12	$922.10	$922.20