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	$152.94	7.644%	$164.6307	$164.63	$164.65	$164.60
Purchase #2	$78.47	12.751%	$88.4757	$88.48	$88.50	$88.50
Purchase #3	$136.36	7.284%	$146.2925	$146.29	$146.30	$146.30
Purchase #4	$62.80	8.104%	$67.8893	$67.89	$67.90	$67.90
Purchase #5	$156.31	3.295%	$161.4604	$161.46	$161.45	$161.50
Purchase #6	$65.26	3.795%	$67.7366	$67.74	$67.75	$67.70
Purchase #7	$91.81	3.632%	$95.1445	$95.14	$95.15	$95.10
7 purchase totals =	$743.95		$791.6297	$791.63	$791.70	$791.60