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	$196.38	10.258%	$216.5247	$216.52	$216.50	$216.50
Purchase #2	$86.51	6.239%	$91.9074	$91.91	$91.90	$91.90
Purchase #3	$29.73	6.459%	$31.6503	$31.65	$31.65	$31.70
Purchase #4	$185.26	6.250%	$196.8388	$196.84	$196.85	$196.80
Purchase #5	$89.32	5.751%	$94.4568	$94.46	$94.45	$94.50
Purchase #6	$146.80	4.667%	$153.6512	$153.65	$153.65	$153.70
Purchase #7	$138.40	13.224%	$156.702	$156.70	$156.70	$156.70
7 purchase totals =	$872.40		$941.7312	$941.73	$941.70	$941.80