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	$244.71	3.816%	$254.0481	$254.05	$254.05	$254.00
Purchase #2	$121.73	9.349%	$133.1105	$133.11	$133.10	$133.10
Purchase #3	$77.49	10.158%	$85.3614	$85.36	$85.35	$85.40
Purchase #4	$245.35	11.470%	$273.4916	$273.49	$273.50	$273.50
Purchase #5	$81.75	11.790%	$91.3883	$91.39	$91.40	$91.40
Purchase #6	$68.76	5.569%	$72.5892	$72.59	$72.60	$72.60
Purchase #7	$57.60	8.382%	$62.428	$62.43	$62.45	$62.40
7 purchase totals =	$897.39		$972.4171	$972.42	$972.45	$972.40