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	$122.55	7.635%	$131.9067	$131.91	$131.90	$131.90
Purchase #2	$136.33	8.279%	$147.6168	$147.62	$147.60	$147.60
Purchase #3	$202.84	4.144%	$211.2457	$211.25	$211.25	$211.20
Purchase #4	$211.82	6.402%	$225.3807	$225.38	$225.40	$225.40
Purchase #5	$93.59	7.609%	$100.7113	$100.71	$100.70	$100.70
Purchase #6	$133.92	5.387%	$141.1343	$141.13	$141.15	$141.10
Purchase #7	$183.56	13.637%	$208.5921	$208.59	$208.60	$208.60
7 purchase totals =	$1,084.61		$1,166.5876	$1,166.59	$1,166.60	$1,166.50