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	$247.54	11.199%	$275.262	$275.26	$275.25	$275.30
Purchase #2	$188.93	6.331%	$200.8912	$200.89	$200.90	$200.90
Purchase #3	$17.42	4.180%	$18.1482	$18.15	$18.15	$18.10
Purchase #4	$90.49	4.514%	$94.5747	$94.57	$94.55	$94.60
Purchase #5	$105.92	3.847%	$109.9947	$109.99	$110.00	$110.00
Purchase #6	$229.50	6.282%	$243.9172	$243.92	$243.90	$243.90
Purchase #7	$71.36	3.515%	$73.8683	$73.87	$73.85	$73.90
7 purchase totals =	$951.16		$1,016.6563	$1,016.65	$1,016.60	$1,016.70