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	$170.64	5.227%	$179.5594	$179.56	$179.55	$179.60
Purchase #2	$173.93	5.256%	$183.0718	$183.07	$183.05	$183.10
Purchase #3	$166.52	5.637%	$175.9067	$175.91	$175.90	$175.90
Purchase #4	$98.40	7.788%	$106.0634	$106.06	$106.05	$106.10
Purchase #5	$218.56	6.713%	$233.2319	$233.23	$233.25	$233.20
Purchase #6	$40.57	12.722%	$45.7313	$45.73	$45.75	$45.70
Purchase #7	$77.88	3.218%	$80.3862	$80.39	$80.40	$80.40
7 purchase totals =	$946.50		$1,003.9507	$1,003.95	$1,003.95	$1,004.00