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	$96.41	4.259%	$100.5161	$100.52	$100.50	$100.50
Purchase #2	$245.75	6.745%	$262.3258	$262.33	$262.35	$262.30
Purchase #3	$153.74	5.674%	$162.4632	$162.46	$162.45	$162.50
Purchase #4	$50.75	12.869%	$57.281	$57.28	$57.30	$57.30
Purchase #5	$62.49	10.427%	$69.0058	$69.01	$69.00	$69.00
Purchase #6	$87.77	3.141%	$90.5269	$90.53	$90.55	$90.50
Purchase #7	$137.25	7.205%	$147.1389	$147.14	$147.15	$147.10
7 purchase totals =	$834.16		$889.2577	$889.27	$889.30	$889.20