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	$25.49	13.117%	$28.8335	$28.83	$28.85	$28.80
Purchase #2	$174.30	12.666%	$196.3768	$196.38	$196.40	$196.40
Purchase #3	$5.47	5.648%	$5.7789	$5.78	$5.80	$5.80
Purchase #4	$149.83	7.753%	$161.4463	$161.45	$161.45	$161.40
Purchase #5	$165.32	13.782%	$188.1044	$188.10	$188.10	$188.10
Purchase #6	$39.53	8.800%	$43.0086	$43.01	$43.00	$43.00
Purchase #7	$74.79	5.282%	$78.7404	$78.74	$78.75	$78.70
7 purchase totals =	$634.73		$702.2889	$702.29	$702.35	$702.20