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	$93.91	5.660%	$99.2253	$99.23	$99.25	$99.20
Purchase #2	$249.69	5.640%	$263.7725	$263.77	$263.75	$263.80
Purchase #3	$191.39	9.870%	$210.2802	$210.28	$210.30	$210.30
Purchase #4	$69.66	4.370%	$72.7041	$72.70	$72.70	$72.70
Purchase #5	$35.29	5.243%	$37.1403	$37.14	$37.15	$37.10
Purchase #6	$249.27	13.434%	$282.7569	$282.76	$282.75	$282.80
Purchase #7	$173.45	10.170%	$191.0899	$191.09	$191.10	$191.10
7 purchase totals =	$1,062.66		$1,156.9692	$1,156.97	$1,157.00	$1,157.00