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	$217.79	11.374%	$242.5614	$242.56	$242.55	$242.60
Purchase #2	$164.42	4.494%	$171.809	$171.81	$171.80	$171.80
Purchase #3	$147.73	4.450%	$154.304	$154.30	$154.30	$154.30
Purchase #4	$41.66	10.549%	$46.0547	$46.05	$46.05	$46.10
Purchase #5	$162.57	5.118%	$170.8903	$170.89	$170.90	$170.90
Purchase #6	$96.30	4.448%	$100.5834	$100.58	$100.60	$100.60
Purchase #7	$121.94	12.454%	$137.1264	$137.13	$137.15	$137.10
7 purchase totals =	$952.41		$1,023.3292	$1,023.32	$1,023.35	$1,023.40