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	$182.26	4.548%	$190.5492	$190.55	$190.55	$190.50
Purchase #2	$158.64	10.586%	$175.4336	$175.43	$175.45	$175.40
Purchase #3	$203.94	7.797%	$219.8412	$219.84	$219.85	$219.80
Purchase #4	$86.92	13.787%	$98.9037	$98.90	$98.90	$98.90
Purchase #5	$99.42	10.396%	$109.7557	$109.76	$109.75	$109.80
Purchase #6	$83.87	5.483%	$88.4686	$88.47	$88.45	$88.50
Purchase #7	$191.42	13.122%	$216.5381	$216.54	$216.55	$216.50
7 purchase totals =	$1,006.47		$1,099.4901	$1,099.49	$1,099.50	$1,099.40