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	$245.26	11.824%	$274.2595	$274.26	$274.25	$274.30
Purchase #2	$178.66	11.139%	$198.5609	$198.56	$198.55	$198.60
Purchase #3	$178.49	10.115%	$196.5443	$196.54	$196.55	$196.50
Purchase #4	$89.72	3.176%	$92.5695	$92.57	$92.55	$92.60
Purchase #5	$26.53	10.562%	$29.3321	$29.33	$29.35	$29.30
Purchase #6	$202.53	4.533%	$211.7107	$211.71	$211.70	$211.70
Purchase #7	$83.56	11.212%	$92.9287	$92.93	$92.95	$92.90
7 purchase totals =	$1,004.75		$1,095.9057	$1,095.90	$1,095.90	$1,095.90