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	$56.56	10.802%	$62.6696	$62.67	$62.65	$62.70
Purchase #2	$92.46	8.495%	$100.3145	$100.31	$100.30	$100.30
Purchase #3	$135.82	9.156%	$148.2557	$148.26	$148.25	$148.30
Purchase #4	$166.48	11.661%	$185.8932	$185.89	$185.90	$185.90
Purchase #5	$115.93	7.400%	$124.5088	$124.51	$124.50	$124.50
Purchase #6	$194.50	7.787%	$209.6457	$209.65	$209.65	$209.60
Purchase #7	$176.34	6.125%	$187.1408	$187.14	$187.15	$187.10
7 purchase totals =	$938.09		$1,018.4283	$1,018.43	$1,018.40	$1,018.40