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	$41.81	9.314%	$45.7042	$45.70	$45.70	$45.70
Purchase #2	$106.33	11.633%	$118.6994	$118.70	$118.70	$118.70
Purchase #3	$39.26	10.560%	$43.4059	$43.41	$43.40	$43.40
Purchase #4	$92.27	7.582%	$99.2659	$99.27	$99.25	$99.30
Purchase #5	$44.69	9.138%	$48.7738	$48.77	$48.75	$48.80
Purchase #6	$131.46	12.639%	$148.0752	$148.08	$148.10	$148.10
Purchase #7	$47.47	7.626%	$51.0901	$51.09	$51.10	$51.10
7 purchase totals =	$503.29		$555.0145	$555.02	$555.00	$555.10