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	$85.78	4.275%	$89.4471	$89.45	$89.45	$89.40
Purchase #2	$221.97	9.406%	$242.8485	$242.85	$242.85	$242.80
Purchase #3	$50.61	5.490%	$53.3885	$53.39	$53.40	$53.40
Purchase #4	$243.42	6.711%	$259.7559	$259.76	$259.75	$259.80
Purchase #5	$172.60	7.567%	$185.6606	$185.66	$185.65	$185.70
Purchase #6	$88.73	12.436%	$99.7645	$99.76	$99.75	$99.80
Purchase #7	$248.60	13.305%	$281.6762	$281.68	$281.70	$281.70
7 purchase totals =	$1,111.71		$1,212.5413	$1,212.55	$1,212.55	$1,212.60