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	$48.28	13.309%	$54.7056	$54.71	$54.70	$54.70
Purchase #2	$98.56	11.236%	$109.6342	$109.63	$109.65	$109.60
Purchase #3	$131.87	3.173%	$136.0542	$136.05	$136.05	$136.10
Purchase #4	$235.71	6.351%	$250.6799	$250.68	$250.70	$250.70
Purchase #5	$85.43	8.430%	$92.6317	$92.63	$92.65	$92.60
Purchase #6	$123.69	7.441%	$132.8938	$132.89	$132.90	$132.90
Purchase #7	$168.98	13.801%	$192.3009	$192.30	$192.30	$192.30
7 purchase totals =	$892.52		$968.9003	$968.89	$968.95	$968.90