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	$202.29	4.710%	$211.8179	$211.82	$211.80	$211.80
Purchase #2	$25.73	11.792%	$28.7641	$28.76	$28.75	$28.80
Purchase #3	$72.47	6.108%	$76.8965	$76.90	$76.90	$76.90
Purchase #4	$184.94	6.188%	$196.3841	$196.38	$196.40	$196.40
Purchase #5	$13.62	6.625%	$14.5223	$14.52	$14.50	$14.50
Purchase #6	$24.44	8.430%	$26.5003	$26.50	$26.50	$26.50
Purchase #7	$38.62	12.311%	$43.3745	$43.37	$43.35	$43.40
7 purchase totals =	$562.11		$598.2597	$598.25	$598.20	$598.30