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	$10.61	5.574%	$11.2014	$11.20	$11.20	$11.20
Purchase #2	$70.39	9.137%	$76.8215	$76.82	$76.80	$76.80
Purchase #3	$100.33	10.629%	$110.9941	$110.99	$111.00	$111.00
Purchase #4	$26.74	8.371%	$28.9784	$28.98	$29.00	$29.00
Purchase #5	$39.71	6.280%	$42.2038	$42.20	$42.20	$42.20
Purchase #6	$31.83	10.505%	$35.1737	$35.17	$35.15	$35.20
Purchase #7	$51.71	5.409%	$54.507	$54.51	$54.50	$54.50
7 purchase totals =	$331.32		$359.8799	$359.87	$359.85	$359.90