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	$127.33	10.825%	$141.1135	$141.11	$141.10	$141.10
Purchase #2	$107.46	5.640%	$113.5207	$113.52	$113.50	$113.50
Purchase #3	$237.62	9.804%	$260.9163	$260.92	$260.90	$260.90
Purchase #4	$174.77	9.195%	$190.8401	$190.84	$190.85	$190.80
Purchase #5	$109.42	12.544%	$123.1456	$123.15	$123.15	$123.10
Purchase #6	$210.59	7.244%	$225.8451	$225.85	$225.85	$225.80
Purchase #7	$126.94	7.309%	$136.218	$136.22	$136.20	$136.20
7 purchase totals =	$1,094.13		$1,191.5993	$1,191.61	$1,191.55	$1,191.40