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	$174.60	6.456%	$185.8722	$185.87	$185.85	$185.90
Purchase #2	$164.71	5.609%	$173.9486	$173.95	$173.95	$173.90
Purchase #3	$234.88	4.506%	$245.4637	$245.46	$245.45	$245.50
Purchase #4	$247.61	11.299%	$275.5875	$275.59	$275.60	$275.60
Purchase #5	$80.59	7.103%	$86.3143	$86.31	$86.30	$86.30
Purchase #6	$92.57	11.382%	$103.1063	$103.11	$103.10	$103.10
Purchase #7	$32.26	4.837%	$33.8204	$33.82	$33.80	$33.80
7 purchase totals =	$1,027.22		$1,104.1130	$1,104.11	$1,104.05	$1,104.10