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	$204.77	5.541%	$216.1163	$216.12	$216.10	$216.10
Purchase #2	$201.41	10.757%	$223.0757	$223.08	$223.10	$223.10
Purchase #3	$93.53	6.404%	$99.5197	$99.52	$99.50	$99.50
Purchase #4	$235.46	6.711%	$251.2617	$251.26	$251.25	$251.30
Purchase #5	$54.46	6.198%	$57.8354	$57.84	$57.85	$57.80
Purchase #6	$143.30	13.290%	$162.3446	$162.34	$162.35	$162.30
Purchase #7	$31.25	13.452%	$35.4538	$35.45	$35.45	$35.50
7 purchase totals =	$964.18		$1,045.6072	$1,045.61	$1,045.60	$1,045.60