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	$194.64	6.244%	$206.7933	$206.79	$206.80	$206.80
Purchase #2	$155.45	10.588%	$171.909	$171.91	$171.90	$171.90
Purchase #3	$141.32	8.105%	$152.774	$152.77	$152.75	$152.80
Purchase #4	$97.59	3.194%	$100.707	$100.71	$100.70	$100.70
Purchase #5	$243.93	12.817%	$275.1945	$275.19	$275.20	$275.20
Purchase #6	$126.42	7.825%	$136.3124	$136.31	$136.30	$136.30
Purchase #7	$123.61	5.772%	$130.7448	$130.74	$130.75	$130.70
7 purchase totals =	$1,082.96		$1,174.4350	$1,174.42	$1,174.40	$1,174.40