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	$9.79	11.671%	$10.9326	$10.93	$10.95	$10.90
Purchase #2	$47.36	7.465%	$50.8954	$50.90	$50.90	$50.90
Purchase #3	$97.41	4.175%	$101.4769	$101.48	$101.50	$101.50
Purchase #4	$85.48	5.854%	$90.484	$90.48	$90.50	$90.50
Purchase #5	$177.67	11.597%	$198.2744	$198.27	$198.25	$198.30
Purchase #6	$103.58	11.532%	$115.5248	$115.52	$115.50	$115.50
Purchase #7	$111.91	13.691%	$127.2316	$127.23	$127.25	$127.20
7 purchase totals =	$633.20		$694.8197	$694.81	$694.85	$694.80