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	$242.51	11.640%	$270.7382	$270.74	$270.75	$270.70
Purchase #2	$33.54	12.767%	$37.8221	$37.82	$37.80	$37.80
Purchase #3	$151.61	11.761%	$169.4409	$169.44	$169.45	$169.40
Purchase #4	$134.49	5.702%	$142.1586	$142.16	$142.15	$142.20
Purchase #5	$176.46	7.590%	$189.8533	$189.85	$189.85	$189.90
Purchase #6	$69.84	4.170%	$72.7523	$72.75	$72.75	$72.80
Purchase #7	$214.38	6.128%	$227.5172	$227.52	$227.50	$227.50
7 purchase totals =	$1,022.83		$1,110.2826	$1,110.28	$1,110.25	$1,110.30