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	$54.54	13.250%	$61.7666	$61.77	$61.75	$61.80
Purchase #2	$63.43	8.253%	$68.6649	$68.66	$68.65	$68.70
Purchase #3	$134.86	13.220%	$152.6885	$152.69	$152.70	$152.70
Purchase #4	$145.72	11.350%	$162.2592	$162.26	$162.25	$162.30
Purchase #5	$6.69	9.516%	$7.3266	$7.33	$7.35	$7.30
Purchase #6	$145.53	13.696%	$165.4618	$165.46	$165.45	$165.50
Purchase #7	$245.27	12.250%	$275.3156	$275.32	$275.30	$275.30
7 purchase totals =	$796.04		$893.4832	$893.49	$893.45	$893.60