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	$136.46	12.656%	$153.7304	$153.73	$153.75	$153.70
Purchase #2	$85.45	11.503%	$95.2793	$95.28	$95.30	$95.30
Purchase #3	$160.38	6.802%	$171.289	$171.29	$171.30	$171.30
Purchase #4	$154.95	5.116%	$162.8772	$162.88	$162.90	$162.90
Purchase #5	$32.33	12.553%	$36.3884	$36.39	$36.40	$36.40
Purchase #6	$144.87	5.237%	$152.4568	$152.46	$152.45	$152.50
Purchase #7	$127.27	9.782%	$139.7196	$139.72	$139.70	$139.70
7 purchase totals =	$841.71		$911.7407	$911.75	$911.80	$911.80