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	$94.61	4.614%	$98.9753	$98.98	$99.00	$99.00
Purchase #2	$50.48	4.428%	$52.7153	$52.72	$52.70	$52.70
Purchase #3	$139.86	8.430%	$151.6502	$151.65	$151.65	$151.70
Purchase #4	$181.98	7.510%	$195.6467	$195.65	$195.65	$195.60
Purchase #5	$60.42	12.138%	$67.7538	$67.75	$67.75	$67.80
Purchase #6	$219.79	8.413%	$238.2809	$238.28	$238.30	$238.30
Purchase #7	$238.63	7.298%	$256.0452	$256.05	$256.05	$256.00
7 purchase totals =	$985.77		$1,061.0674	$1,061.08	$1,061.10	$1,061.10