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	$84.44	10.568%	$93.3636	$93.36	$93.35	$93.40
Purchase #2	$129.59	9.872%	$142.3831	$142.38	$142.40	$142.40
Purchase #3	$94.29	7.281%	$101.1553	$101.16	$101.15	$101.20
Purchase #4	$30.33	11.540%	$33.8301	$33.83	$33.85	$33.80
Purchase #5	$231.66	9.512%	$253.6955	$253.70	$253.70	$253.70
Purchase #6	$194.54	10.818%	$215.5853	$215.59	$215.60	$215.60
Purchase #7	$101.32	9.802%	$111.2514	$111.25	$111.25	$111.30
7 purchase totals =	$866.17		$951.2643	$951.27	$951.30	$951.40