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	$119.37	4.700%	$124.9804	$124.98	$125.00	$125.00
Purchase #2	$216.41	8.701%	$235.2398	$235.24	$235.25	$235.20
Purchase #3	$124.39	3.105%	$128.2523	$128.25	$128.25	$128.30
Purchase #4	$53.57	11.581%	$59.7739	$59.77	$59.75	$59.80
Purchase #5	$60.46	10.538%	$66.8313	$66.83	$66.85	$66.80
Purchase #6	$249.38	6.777%	$266.2805	$266.28	$266.30	$266.30
Purchase #7	$58.83	13.696%	$66.8874	$66.89	$66.90	$66.90
7 purchase totals =	$882.41		$948.2456	$948.24	$948.30	$948.30