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	$148.68	9.555%	$162.8864	$162.89	$162.90	$162.90
Purchase #2	$135.69	6.549%	$144.5763	$144.58	$144.60	$144.60
Purchase #3	$68.77	3.816%	$71.3943	$71.39	$71.40	$71.40
Purchase #4	$31.38	4.734%	$32.8655	$32.87	$32.85	$32.90
Purchase #5	$71.62	11.114%	$79.5798	$79.58	$79.60	$79.60
Purchase #6	$166.35	9.167%	$181.5993	$181.60	$181.60	$181.60
Purchase #7	$23.57	9.549%	$25.8207	$25.82	$25.80	$25.80
7 purchase totals =	$646.06		$698.7223	$698.73	$698.75	$698.80