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	$82.60	13.562%	$93.8022	$93.80	$93.80	$93.80
Purchase #2	$52.34	13.245%	$59.2724	$59.27	$59.25	$59.30
Purchase #3	$223.53	8.662%	$242.8922	$242.89	$242.90	$242.90
Purchase #4	$88.53	4.349%	$92.3802	$92.38	$92.40	$92.40
Purchase #5	$57.36	13.480%	$65.0921	$65.09	$65.10	$65.10
Purchase #6	$80.84	9.516%	$88.5327	$88.53	$88.55	$88.50
Purchase #7	$33.31	5.801%	$35.2423	$35.24	$35.25	$35.20
7 purchase totals =	$618.51		$677.2141	$677.20	$677.25	$677.20