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	$235.44	11.379%	$262.2307	$262.23	$262.25	$262.20
Purchase #2	$133.33	13.615%	$151.4829	$151.48	$151.50	$151.50
Purchase #3	$86.34	6.750%	$92.168	$92.17	$92.15	$92.20
Purchase #4	$65.79	8.152%	$71.1532	$71.15	$71.15	$71.20
Purchase #5	$90.33	10.372%	$99.699	$99.70	$99.70	$99.70
Purchase #6	$192.44	3.263%	$198.7193	$198.72	$198.70	$198.70
Purchase #7	$129.79	8.133%	$140.3458	$140.35	$140.35	$140.30
7 purchase totals =	$933.46		$1,015.7989	$1,015.80	$1,015.80	$1,015.80