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	$231.27	6.237%	$245.6943	$245.69	$245.70	$245.70
Purchase #2	$9.91	13.838%	$11.2813	$11.28	$11.30	$11.30
Purchase #3	$37.53	13.147%	$42.4641	$42.46	$42.45	$42.50
Purchase #4	$238.55	10.866%	$264.4708	$264.47	$264.45	$264.50
Purchase #5	$133.60	13.817%	$152.0595	$152.06	$152.05	$152.10
Purchase #6	$40.50	11.384%	$45.1105	$45.11	$45.10	$45.10
Purchase #7	$249.69	7.387%	$268.1346	$268.13	$268.15	$268.10
7 purchase totals =	$941.05		$1,029.2151	$1,029.20	$1,029.20	$1,029.30