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	$48.33	5.351%	$50.9161	$50.92	$50.90	$50.90
Purchase #2	$26.99	10.559%	$29.8399	$29.84	$29.85	$29.80
Purchase #3	$150.47	12.237%	$168.883	$168.88	$168.90	$168.90
Purchase #4	$119.81	5.558%	$126.469	$126.47	$126.45	$126.50
Purchase #5	$216.48	3.117%	$223.2277	$223.23	$223.25	$223.20
Purchase #6	$59.53	8.198%	$64.4103	$64.41	$64.40	$64.40
Purchase #7	$85.48	13.303%	$96.8514	$96.85	$96.85	$96.90
7 purchase totals =	$707.09		$760.5974	$760.60	$760.60	$760.60