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	$115.59	10.225%	$127.4091	$127.41	$127.40	$127.40
Purchase #2	$83.94	6.267%	$89.2005	$89.20	$89.20	$89.20
Purchase #3	$50.87	13.305%	$57.6383	$57.64	$57.65	$57.60
Purchase #4	$46.30	6.398%	$49.2623	$49.26	$49.25	$49.30
Purchase #5	$147.50	12.314%	$165.6632	$165.66	$165.65	$165.70
Purchase #6	$84.28	13.454%	$95.619	$95.62	$95.60	$95.60
Purchase #7	$115.88	9.867%	$127.3139	$127.31	$127.30	$127.30
7 purchase totals =	$644.36		$712.1063	$712.10	$712.05	$712.10