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	$185.80	13.751%	$211.3494	$211.35	$211.35	$211.30
Purchase #2	$183.91	3.800%	$190.8986	$190.90	$190.90	$190.90
Purchase #3	$238.31	3.355%	$246.3053	$246.31	$246.30	$246.30
Purchase #4	$6.56	11.774%	$7.3324	$7.33	$7.35	$7.30
Purchase #5	$128.70	13.649%	$146.2663	$146.27	$146.25	$146.30
Purchase #6	$68.76	8.855%	$74.8487	$74.85	$74.85	$74.80
Purchase #7	$178.54	3.275%	$184.3872	$184.39	$184.40	$184.40
7 purchase totals =	$990.58		$1,061.3879	$1,061.40	$1,061.40	$1,061.30