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	$170.89	13.505%	$193.9687	$193.97	$193.95	$194.00
Purchase #2	$28.75	11.868%	$32.1621	$32.16	$32.15	$32.20
Purchase #3	$101.63	13.155%	$114.9994	$115.00	$115.00	$115.00
Purchase #4	$181.50	9.308%	$198.394	$198.39	$198.40	$198.40
Purchase #5	$130.73	8.316%	$141.6015	$141.60	$141.60	$141.60
Purchase #6	$247.89	3.380%	$256.2687	$256.27	$256.25	$256.30
Purchase #7	$160.62	7.314%	$172.3677	$172.37	$172.35	$172.40
7 purchase totals =	$1,022.01		$1,109.7621	$1,109.76	$1,109.70	$1,109.90