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	$93.52	8.423%	$101.3972	$101.40	$101.40	$101.40
Purchase #2	$72.49	8.663%	$78.7698	$78.77	$78.75	$78.80
Purchase #3	$106.49	10.512%	$117.6842	$117.68	$117.70	$117.70
Purchase #4	$167.95	9.823%	$184.4477	$184.45	$184.45	$184.40
Purchase #5	$179.58	6.512%	$191.2742	$191.27	$191.25	$191.30
Purchase #6	$244.98	10.277%	$270.1566	$270.16	$270.15	$270.20
Purchase #7	$208.46	6.640%	$222.3017	$222.30	$222.30	$222.30
7 purchase totals =	$1,073.47		$1,166.0314	$1,166.03	$1,166.00	$1,166.10