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	$156.96	11.497%	$175.0057	$175.01	$175.00	$175.00
Purchase #2	$164.33	11.368%	$183.011	$183.01	$183.00	$183.00
Purchase #3	$39.48	8.742%	$42.9313	$42.93	$42.95	$42.90
Purchase #4	$146.68	7.420%	$157.5637	$157.56	$157.55	$157.60
Purchase #5	$30.46	8.244%	$32.9711	$32.97	$32.95	$33.00
Purchase #6	$212.63	4.632%	$222.479	$222.48	$222.50	$222.50
Purchase #7	$68.27	6.184%	$72.4918	$72.49	$72.50	$72.50
7 purchase totals =	$818.81		$886.4536	$886.45	$886.45	$886.50