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	$217.45	12.258%	$244.105	$244.11	$244.10	$244.10
Purchase #2	$112.60	7.392%	$120.9234	$120.92	$120.90	$120.90
Purchase #3	$137.48	7.443%	$147.7126	$147.71	$147.70	$147.70
Purchase #4	$76.89	8.676%	$83.561	$83.56	$83.55	$83.60
Purchase #5	$163.93	11.210%	$182.3066	$182.31	$182.30	$182.30
Purchase #6	$62.43	4.237%	$65.0752	$65.08	$65.10	$65.10
Purchase #7	$249.38	7.369%	$267.7568	$267.76	$267.75	$267.80
7 purchase totals =	$1,020.16		$1,111.4406	$1,111.45	$1,111.40	$1,111.50