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	$177.32	4.838%	$185.8987	$185.90	$185.90	$185.90
Purchase #2	$65.56	3.545%	$67.8841	$67.88	$67.90	$67.90
Purchase #3	$123.26	5.658%	$130.2341	$130.23	$130.25	$130.20
Purchase #4	$37.78	13.612%	$42.9226	$42.92	$42.90	$42.90
Purchase #5	$28.63	7.459%	$30.7655	$30.77	$30.75	$30.80
Purchase #6	$65.53	11.551%	$73.0994	$73.10	$73.10	$73.10
Purchase #7	$13.94	5.326%	$14.6824	$14.68	$14.70	$14.70
7 purchase totals =	$512.02		$545.4868	$545.48	$545.50	$545.50