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	$176.31	3.277%	$182.0877	$182.09	$182.10	$182.10
Purchase #2	$126.86	10.624%	$140.3376	$140.34	$140.35	$140.30
Purchase #3	$245.61	6.130%	$260.6659	$260.67	$260.65	$260.70
Purchase #4	$217.27	5.320%	$228.8288	$228.83	$228.85	$228.80
Purchase #5	$90.76	9.867%	$99.7153	$99.72	$99.70	$99.70
Purchase #6	$97.59	9.794%	$107.148	$107.15	$107.15	$107.10
Purchase #7	$160.54	11.838%	$179.5447	$179.54	$179.55	$179.50
7 purchase totals =	$1,114.94		$1,198.3280	$1,198.34	$1,198.35	$1,198.20