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	$58.31	5.617%	$61.5853	$61.59	$61.60	$61.60
Purchase #2	$170.56	8.148%	$184.4572	$184.46	$184.45	$184.50
Purchase #3	$43.50	11.219%	$48.3803	$48.38	$48.40	$48.40
Purchase #4	$28.33	6.390%	$30.1403	$30.14	$30.15	$30.10
Purchase #5	$163.33	9.607%	$179.0211	$179.02	$179.00	$179.00
Purchase #6	$42.56	5.695%	$44.9838	$44.98	$45.00	$45.00
Purchase #7	$53.92	11.861%	$60.3155	$60.32	$60.30	$60.30
7 purchase totals =	$560.51		$608.8835	$608.89	$608.90	$608.90