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	$179.55	3.375%	$185.6098	$185.61	$185.60	$185.60
Purchase #2	$160.61	3.302%	$165.9133	$165.91	$165.90	$165.90
Purchase #3	$81.94	3.803%	$85.0562	$85.06	$85.05	$85.10
Purchase #4	$75.98	3.648%	$78.7518	$78.75	$78.75	$78.80
Purchase #5	$119.29	10.816%	$132.1924	$132.19	$132.20	$132.20
Purchase #6	$47.76	13.648%	$54.2783	$54.28	$54.30	$54.30
Purchase #7	$218.74	13.329%	$247.8959	$247.90	$247.90	$247.90
7 purchase totals =	$883.87		$949.6977	$949.70	$949.70	$949.80