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	$70.39	11.789%	$78.6883	$78.69	$78.70	$78.70
Purchase #2	$126.72	10.739%	$140.3285	$140.33	$140.35	$140.30
Purchase #3	$217.25	10.388%	$239.8179	$239.82	$239.80	$239.80
Purchase #4	$112.32	5.270%	$118.2393	$118.24	$118.25	$118.20
Purchase #5	$143.45	5.471%	$151.2981	$151.30	$151.30	$151.30
Purchase #6	$103.45	5.380%	$109.0156	$109.02	$109.00	$109.00
Purchase #7	$165.96	13.573%	$188.4858	$188.49	$188.50	$188.50
7 purchase totals =	$939.54		$1,025.8735	$1,025.89	$1,025.90	$1,025.80