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	$235.37	8.279%	$254.8563	$254.86	$254.85	$254.90
Purchase #2	$98.72	4.728%	$103.3875	$103.39	$103.40	$103.40
Purchase #3	$31.30	7.103%	$33.5232	$33.52	$33.50	$33.50
Purchase #4	$185.29	11.242%	$206.1203	$206.12	$206.10	$206.10
Purchase #5	$128.30	8.222%	$138.8488	$138.85	$138.85	$138.80
Purchase #6	$219.27	7.489%	$235.6911	$235.69	$235.70	$235.70
Purchase #7	$105.27	8.463%	$114.179	$114.18	$114.20	$114.20
7 purchase totals =	$1,003.52		$1,086.6062	$1,086.61	$1,086.60	$1,086.60