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	$153.77	7.606%	$165.4657	$165.47	$165.45	$165.50
Purchase #2	$52.40	4.309%	$54.6579	$54.66	$54.65	$54.70
Purchase #3	$65.33	11.858%	$73.0768	$73.08	$73.10	$73.10
Purchase #4	$88.85	12.268%	$99.7501	$99.75	$99.75	$99.80
Purchase #5	$93.82	5.839%	$99.2981	$99.30	$99.30	$99.30
Purchase #6	$223.37	13.670%	$253.9047	$253.90	$253.90	$253.90
Purchase #7	$147.37	12.586%	$165.918	$165.92	$165.90	$165.90
7 purchase totals =	$824.91		$912.0713	$912.08	$912.05	$912.20