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	$158.27	12.238%	$177.6391	$177.64	$177.65	$177.60
Purchase #2	$59.63	5.525%	$62.9246	$62.92	$62.90	$62.90
Purchase #3	$68.59	3.378%	$70.907	$70.91	$70.90	$70.90
Purchase #4	$32.44	3.323%	$33.518	$33.52	$33.50	$33.50
Purchase #5	$149.61	13.404%	$169.6637	$169.66	$169.65	$169.70
Purchase #6	$145.78	10.216%	$160.6729	$160.67	$160.65	$160.70
Purchase #7	$75.55	13.281%	$85.5838	$85.58	$85.60	$85.60
7 purchase totals =	$689.87		$760.9091	$760.90	$760.85	$760.90