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	$168.86	3.184%	$174.2365	$174.24	$174.25	$174.20
Purchase #2	$71.73	13.333%	$81.2938	$81.29	$81.30	$81.30
Purchase #3	$244.45	10.217%	$269.4255	$269.43	$269.45	$269.40
Purchase #4	$206.84	13.794%	$235.3715	$235.37	$235.35	$235.40
Purchase #5	$219.28	10.571%	$242.4601	$242.46	$242.45	$242.50
Purchase #6	$66.59	7.820%	$71.7973	$71.80	$71.80	$71.80
Purchase #7	$218.48	11.376%	$243.3343	$243.33	$243.35	$243.30
7 purchase totals =	$1,196.23		$1,317.9190	$1,317.92	$1,317.95	$1,317.90