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	$247.78	5.435%	$261.2468	$261.25	$261.25	$261.20
Purchase #2	$45.87	4.391%	$47.8842	$47.88	$47.90	$47.90
Purchase #3	$115.61	4.163%	$120.4228	$120.42	$120.40	$120.40
Purchase #4	$213.27	13.204%	$241.4302	$241.43	$241.45	$241.40
Purchase #5	$71.31	10.109%	$78.5187	$78.52	$78.50	$78.50
Purchase #6	$74.88	8.711%	$81.4028	$81.40	$81.40	$81.40
Purchase #7	$93.90	5.617%	$99.1744	$99.17	$99.15	$99.20
7 purchase totals =	$862.62		$930.0799	$930.07	$930.05	$930.00