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	$108.61	12.464%	$122.1472	$122.15	$122.15	$122.10
Purchase #2	$118.43	4.394%	$123.6338	$123.63	$123.65	$123.60
Purchase #3	$219.89	4.394%	$229.552	$229.55	$229.55	$229.60
Purchase #4	$168.74	8.407%	$182.926	$182.93	$182.95	$182.90
Purchase #5	$130.89	3.802%	$135.8664	$135.87	$135.85	$135.90
Purchase #6	$52.95	8.591%	$57.4989	$57.50	$57.50	$57.50
Purchase #7	$227.38	9.448%	$248.8629	$248.86	$248.85	$248.90
7 purchase totals =	$1,026.89		$1,100.4872	$1,100.49	$1,100.50	$1,100.50