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	$168.75	12.797%	$190.3449	$190.34	$190.35	$190.30
Purchase #2	$35.56	9.479%	$38.9307	$38.93	$38.95	$38.90
Purchase #3	$218.65	11.183%	$243.1016	$243.10	$243.10	$243.10
Purchase #4	$156.92	7.210%	$168.2339	$168.23	$168.25	$168.20
Purchase #5	$183.77	11.862%	$205.5688	$205.57	$205.55	$205.60
Purchase #6	$45.52	10.593%	$50.3419	$50.34	$50.35	$50.30
Purchase #7	$148.50	4.255%	$154.8187	$154.82	$154.80	$154.80
7 purchase totals =	$957.67		$1,051.3405	$1,051.33	$1,051.35	$1,051.20