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	$35.44	6.338%	$37.6862	$37.69	$37.70	$37.70
Purchase #2	$246.36	7.461%	$264.7409	$264.74	$264.75	$264.70
Purchase #3	$204.55	7.530%	$219.9526	$219.95	$219.95	$220.00
Purchase #4	$239.51	13.228%	$271.1924	$271.19	$271.20	$271.20
Purchase #5	$104.94	11.230%	$116.7248	$116.72	$116.70	$116.70
Purchase #6	$103.80	7.541%	$111.6276	$111.63	$111.65	$111.60
Purchase #7	$48.70	11.533%	$54.3166	$54.32	$54.30	$54.30
7 purchase totals =	$983.30		$1,076.2411	$1,076.24	$1,076.25	$1,076.20