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	$194.48	7.769%	$209.5892	$209.59	$209.60	$209.60
Purchase #2	$188.85	13.170%	$213.7215	$213.72	$213.70	$213.70
Purchase #3	$42.39	11.268%	$47.1665	$47.17	$47.15	$47.20
Purchase #4	$51.29	4.276%	$53.4832	$53.48	$53.50	$53.50
Purchase #5	$89.77	10.667%	$99.3458	$99.35	$99.35	$99.30
Purchase #6	$160.69	11.601%	$179.3316	$179.33	$179.35	$179.30
Purchase #7	$160.42	10.171%	$176.7363	$176.74	$176.75	$176.70
7 purchase totals =	$887.89		$979.3741	$979.38	$979.40	$979.30