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	$249.56	9.740%	$273.8671	$273.87	$273.85	$273.90
Purchase #2	$237.46	5.349%	$250.1617	$250.16	$250.15	$250.20
Purchase #3	$74.99	5.273%	$78.9442	$78.94	$78.95	$78.90
Purchase #4	$167.87	4.708%	$175.7733	$175.77	$175.75	$175.80
Purchase #5	$38.40	9.564%	$42.0726	$42.07	$42.05	$42.10
Purchase #6	$43.73	11.417%	$48.7227	$48.72	$48.70	$48.70
Purchase #7	$204.44	4.510%	$213.6602	$213.66	$213.65	$213.70
7 purchase totals =	$1,016.45		$1,083.2018	$1,083.19	$1,083.10	$1,083.30