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	$54.90	8.292%	$59.4523	$59.45	$59.45	$59.50
Purchase #2	$168.90	10.743%	$187.0449	$187.04	$187.05	$187.00
Purchase #3	$55.89	12.282%	$62.7544	$62.75	$62.75	$62.80
Purchase #4	$146.58	10.537%	$162.0251	$162.03	$162.05	$162.00
Purchase #5	$146.25	6.109%	$155.1844	$155.18	$155.20	$155.20
Purchase #6	$83.27	13.771%	$94.7371	$94.74	$94.75	$94.70
Purchase #7	$21.72	3.705%	$22.5247	$22.52	$22.50	$22.50
7 purchase totals =	$677.51		$743.7229	$743.71	$743.75	$743.70