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	$148.55	8.136%	$160.636	$160.64	$160.65	$160.60
Purchase #2	$241.58	9.506%	$264.5446	$264.54	$264.55	$264.50
Purchase #3	$221.63	7.323%	$237.86	$237.86	$237.85	$237.90
Purchase #4	$211.87	6.437%	$225.5081	$225.51	$225.50	$225.50
Purchase #5	$188.42	6.332%	$200.3508	$200.35	$200.35	$200.40
Purchase #6	$62.56	11.762%	$69.9183	$69.92	$69.90	$69.90
Purchase #7	$141.30	5.108%	$148.5176	$148.52	$148.50	$148.50
7 purchase totals =	$1,215.91		$1,307.3354	$1,307.34	$1,307.30	$1,307.30