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	$223.80	4.417%	$233.6852	$233.69	$233.70	$233.70
Purchase #2	$118.92	4.465%	$124.2298	$124.23	$124.25	$124.20
Purchase #3	$99.67	5.220%	$104.8728	$104.87	$104.85	$104.90
Purchase #4	$140.87	11.147%	$156.5728	$156.57	$156.55	$156.60
Purchase #5	$112.25	5.121%	$117.9983	$118.00	$118.00	$118.00
Purchase #6	$103.80	5.761%	$109.7799	$109.78	$109.80	$109.80
Purchase #7	$57.64	7.749%	$62.1065	$62.11	$62.10	$62.10
7 purchase totals =	$856.95		$909.2453	$909.25	$909.25	$909.30