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	$194.25	13.185%	$219.8619	$219.86	$219.85	$219.90
Purchase #2	$15.71	11.414%	$17.5031	$17.50	$17.50	$17.50
Purchase #3	$87.56	13.430%	$99.3193	$99.32	$99.30	$99.30
Purchase #4	$66.90	5.127%	$70.33	$70.33	$70.35	$70.30
Purchase #5	$241.99	11.379%	$269.526	$269.53	$269.55	$269.50
Purchase #6	$85.38	12.732%	$96.2506	$96.25	$96.25	$96.30
Purchase #7	$90.68	11.859%	$101.4337	$101.43	$101.45	$101.40
7 purchase totals =	$782.47		$874.2246	$874.22	$874.25	$874.20