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	$185.31	3.811%	$192.3722	$192.37	$192.35	$192.40
Purchase #2	$76.96	3.343%	$79.5328	$79.53	$79.55	$79.50
Purchase #3	$119.28	7.817%	$128.6041	$128.60	$128.60	$128.60
Purchase #4	$130.56	7.147%	$139.8911	$139.89	$139.90	$139.90
Purchase #5	$106.49	9.193%	$116.2796	$116.28	$116.30	$116.30
Purchase #6	$147.34	13.655%	$167.4593	$167.46	$167.45	$167.50
Purchase #7	$121.53	8.170%	$131.459	$131.46	$131.45	$131.50
7 purchase totals =	$887.47		$955.5981	$955.59	$955.60	$955.70