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	$96.37	11.514%	$107.466	$107.47	$107.45	$107.50
Purchase #2	$151.68	13.236%	$171.7564	$171.76	$171.75	$171.80
Purchase #3	$31.96	8.824%	$34.7802	$34.78	$34.80	$34.80
Purchase #4	$149.88	10.494%	$165.6084	$165.61	$165.60	$165.60
Purchase #5	$106.27	7.546%	$114.2891	$114.29	$114.30	$114.30
Purchase #6	$156.68	3.796%	$162.6276	$162.63	$162.65	$162.60
Purchase #7	$221.51	13.268%	$250.8999	$250.90	$250.90	$250.90
7 purchase totals =	$914.35		$1,007.4276	$1,007.44	$1,007.45	$1,007.50