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	$226.82	7.380%	$243.5593	$243.56	$243.55	$243.60
Purchase #2	$60.34	7.319%	$64.7563	$64.76	$64.75	$64.80
Purchase #3	$72.40	8.434%	$78.5062	$78.51	$78.50	$78.50
Purchase #4	$78.56	13.442%	$89.12	$89.12	$89.10	$89.10
Purchase #5	$39.66	9.851%	$43.5669	$43.57	$43.55	$43.60
Purchase #6	$136.77	4.297%	$142.647	$142.65	$142.65	$142.60
Purchase #7	$45.70	11.418%	$50.918	$50.92	$50.90	$50.90
7 purchase totals =	$660.25		$713.0737	$713.09	$713.00	$713.10