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	$245.63	7.659%	$264.4428	$264.44	$264.45	$264.40
Purchase #2	$20.79	11.807%	$23.2447	$23.24	$23.25	$23.20
Purchase #3	$85.85	5.166%	$90.285	$90.29	$90.30	$90.30
Purchase #4	$39.95	8.358%	$43.289	$43.29	$43.30	$43.30
Purchase #5	$81.78	11.454%	$91.1471	$91.15	$91.15	$91.10
Purchase #6	$59.35	8.819%	$64.5841	$64.58	$64.60	$64.60
Purchase #7	$107.61	10.443%	$118.8477	$118.85	$118.85	$118.80
7 purchase totals =	$640.96		$695.8404	$695.84	$695.90	$695.70