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	$148.58	6.671%	$158.4918	$158.49	$158.50	$158.50
Purchase #2	$84.48	6.425%	$89.9078	$89.91	$89.90	$89.90
Purchase #3	$45.68	3.572%	$47.3117	$47.31	$47.30	$47.30
Purchase #4	$160.74	7.801%	$173.2793	$173.28	$173.30	$173.30
Purchase #5	$86.59	10.277%	$95.4889	$95.49	$95.50	$95.50
Purchase #6	$223.81	12.385%	$251.5289	$251.53	$251.55	$251.50
Purchase #7	$171.93	4.758%	$180.1104	$180.11	$180.10	$180.10
7 purchase totals =	$921.81		$996.1188	$996.12	$996.15	$996.10