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	$175.55	12.106%	$196.8021	$196.80	$196.80	$196.80
Purchase #2	$187.77	4.814%	$196.8092	$196.81	$196.80	$196.80
Purchase #3	$46.74	13.825%	$53.2018	$53.20	$53.20	$53.20
Purchase #4	$94.58	4.556%	$98.8891	$98.89	$98.90	$98.90
Purchase #5	$119.92	8.327%	$129.9057	$129.91	$129.90	$129.90
Purchase #6	$77.64	12.165%	$87.0849	$87.08	$87.10	$87.10
Purchase #7	$133.76	10.803%	$148.2101	$148.21	$148.20	$148.20
7 purchase totals =	$835.96		$910.9029	$910.90	$910.90	$910.90