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	$88.86	12.475%	$99.9453	$99.95	$99.95	$99.90
Purchase #2	$79.97	12.171%	$89.7031	$89.70	$89.70	$89.70
Purchase #3	$117.53	8.413%	$127.4178	$127.42	$127.40	$127.40
Purchase #4	$196.78	12.106%	$220.6022	$220.60	$220.60	$220.60
Purchase #5	$165.80	5.619%	$175.1163	$175.12	$175.10	$175.10
Purchase #6	$65.27	7.654%	$70.2658	$70.27	$70.25	$70.30
Purchase #7	$90.38	8.543%	$98.1012	$98.10	$98.10	$98.10
7 purchase totals =	$804.59		$881.1517	$881.16	$881.10	$881.10