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	$74.27	12.535%	$83.5797	$83.58	$83.60	$83.60
Purchase #2	$165.84	11.703%	$185.2483	$185.25	$185.25	$185.20
Purchase #3	$149.91	12.178%	$168.166	$168.17	$168.15	$168.20
Purchase #4	$134.55	12.124%	$150.8628	$150.86	$150.85	$150.90
Purchase #5	$118.82	6.796%	$126.895	$126.90	$126.90	$126.90
Purchase #6	$223.63	7.779%	$241.0262	$241.03	$241.05	$241.00
Purchase #7	$70.76	11.434%	$78.8507	$78.85	$78.85	$78.90
7 purchase totals =	$937.78		$1,034.6287	$1,034.64	$1,034.65	$1,034.70