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	$172.38	4.353%	$179.8837	$179.88	$179.90	$179.90
Purchase #2	$130.76	8.695%	$142.1296	$142.13	$142.15	$142.10
Purchase #3	$51.56	8.262%	$55.8199	$55.82	$55.80	$55.80
Purchase #4	$99.52	7.492%	$106.976	$106.98	$107.00	$107.00
Purchase #5	$109.62	12.305%	$123.1087	$123.11	$123.10	$123.10
Purchase #6	$199.69	11.629%	$222.912	$222.91	$222.90	$222.90
Purchase #7	$151.27	6.472%	$161.0602	$161.06	$161.05	$161.10
7 purchase totals =	$914.80		$991.8901	$991.89	$991.90	$991.90