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	$56.65	8.410%	$61.4143	$61.41	$61.40	$61.40
Purchase #2	$37.29	13.785%	$42.4304	$42.43	$42.45	$42.40
Purchase #3	$168.50	5.503%	$177.7726	$177.77	$177.75	$177.80
Purchase #4	$53.46	4.196%	$55.7032	$55.70	$55.70	$55.70
Purchase #5	$127.38	5.228%	$134.0394	$134.04	$134.05	$134.00
Purchase #6	$219.89	11.582%	$245.3577	$245.36	$245.35	$245.40
Purchase #7	$117.27	12.331%	$131.7306	$131.73	$131.75	$131.70
7 purchase totals =	$780.44		$848.4482	$848.44	$848.45	$848.40