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	$220.88	4.723%	$231.3122	$231.31	$231.30	$231.30
Purchase #2	$105.88	3.107%	$109.1697	$109.17	$109.15	$109.20
Purchase #3	$56.72	6.314%	$60.3013	$60.30	$60.30	$60.30
Purchase #4	$16.60	10.361%	$18.3199	$18.32	$18.30	$18.30
Purchase #5	$83.98	7.657%	$90.4103	$90.41	$90.40	$90.40
Purchase #6	$224.99	4.504%	$235.1235	$235.12	$235.10	$235.10
Purchase #7	$44.38	5.234%	$46.7028	$46.70	$46.70	$46.70
7 purchase totals =	$753.43		$791.3397	$791.33	$791.25	$791.30