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	$240.90	8.523%	$261.4319	$261.43	$261.45	$261.40
Purchase #2	$82.42	10.675%	$91.2183	$91.22	$91.20	$91.20
Purchase #3	$243.68	6.423%	$259.3316	$259.33	$259.35	$259.30
Purchase #4	$98.44	12.856%	$111.0954	$111.10	$111.10	$111.10
Purchase #5	$47.51	3.142%	$49.0028	$49.00	$49.00	$49.00
Purchase #6	$53.72	11.361%	$59.8231	$59.82	$59.80	$59.80
Purchase #7	$105.56	11.529%	$117.73	$117.73	$117.75	$117.70
7 purchase totals =	$872.23		$949.6331	$949.63	$949.65	$949.50