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	$112.60	13.339%	$127.6197	$127.62	$127.60	$127.60
Purchase #2	$135.54	10.860%	$150.2596	$150.26	$150.25	$150.30
Purchase #3	$172.38	7.532%	$185.3637	$185.36	$185.35	$185.40
Purchase #4	$227.46	5.514%	$240.0021	$240.00	$240.00	$240.00
Purchase #5	$219.33	9.495%	$240.1554	$240.16	$240.15	$240.20
Purchase #6	$25.69	10.367%	$28.3533	$28.35	$28.35	$28.40
Purchase #7	$60.58	8.811%	$65.9177	$65.92	$65.90	$65.90
7 purchase totals =	$953.58		$1,037.6715	$1,037.67	$1,037.60	$1,037.80