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	$84.32	11.707%	$94.1913	$94.19	$94.20	$94.20
Purchase #2	$245.72	3.851%	$255.1827	$255.18	$255.20	$255.20
Purchase #3	$112.33	11.203%	$124.9143	$124.91	$124.90	$124.90
Purchase #4	$78.46	9.535%	$85.9412	$85.94	$85.95	$85.90
Purchase #5	$215.81	4.519%	$225.5625	$225.56	$225.55	$225.60
Purchase #6	$138.38	10.872%	$153.4247	$153.42	$153.40	$153.40
Purchase #7	$209.67	11.693%	$234.1867	$234.19	$234.20	$234.20
7 purchase totals =	$1,084.69		$1,173.4034	$1,173.39	$1,173.40	$1,173.40