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	$134.73	11.531%	$150.2657	$150.27	$150.25	$150.30
Purchase #2	$82.85	9.141%	$90.4233	$90.42	$90.40	$90.40
Purchase #3	$216.42	6.783%	$231.0998	$231.10	$231.10	$231.10
Purchase #4	$91.78	8.261%	$99.3619	$99.36	$99.35	$99.40
Purchase #5	$211.45	13.849%	$240.7337	$240.73	$240.75	$240.70
Purchase #6	$167.84	7.143%	$179.8288	$179.83	$179.85	$179.80
Purchase #7	$22.69	9.309%	$24.8022	$24.80	$24.80	$24.80
7 purchase totals =	$927.76		$1,016.5154	$1,016.51	$1,016.50	$1,016.50