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	$149.76	4.792%	$156.9365	$156.94	$156.95	$156.90
Purchase #2	$78.90	7.478%	$84.8001	$84.80	$84.80	$84.80
Purchase #3	$52.69	12.686%	$59.3743	$59.37	$59.35	$59.40
Purchase #4	$56.55	8.487%	$61.3494	$61.35	$61.35	$61.30
Purchase #5	$81.60	8.740%	$88.7318	$88.73	$88.75	$88.70
Purchase #6	$31.61	6.157%	$33.5562	$33.56	$33.55	$33.60
Purchase #7	$186.56	13.525%	$211.7922	$211.79	$211.80	$211.80
7 purchase totals =	$637.67		$696.5405	$696.54	$696.55	$696.50