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	$118.52	8.465%	$128.5527	$128.55	$128.55	$128.60
Purchase #2	$243.69	12.415%	$273.9441	$273.94	$273.95	$273.90
Purchase #3	$40.26	9.123%	$43.9329	$43.93	$43.95	$43.90
Purchase #4	$81.77	10.104%	$90.032	$90.03	$90.05	$90.00
Purchase #5	$74.78	9.355%	$81.7757	$81.78	$81.80	$81.80
Purchase #6	$75.68	6.245%	$80.4062	$80.41	$80.40	$80.40
Purchase #7	$150.32	10.136%	$165.5564	$165.56	$165.55	$165.60
7 purchase totals =	$785.02		$864.2000	$864.20	$864.25	$864.20