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	$167.89	11.808%	$187.7145	$187.71	$187.70	$187.70
Purchase #2	$245.95	12.516%	$276.7331	$276.73	$276.75	$276.70
Purchase #3	$213.57	11.141%	$237.3638	$237.36	$237.35	$237.40
Purchase #4	$141.87	4.305%	$147.9775	$147.98	$148.00	$148.00
Purchase #5	$71.34	8.707%	$77.5516	$77.55	$77.55	$77.60
Purchase #6	$53.27	12.274%	$59.8084	$59.81	$59.80	$59.80
Purchase #7	$194.37	7.614%	$209.1693	$209.17	$209.15	$209.20
7 purchase totals =	$1,088.26		$1,196.3182	$1,196.31	$1,196.30	$1,196.40