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	$169.46	9.611%	$185.7468	$185.75	$185.75	$185.70
Purchase #2	$203.78	13.795%	$231.8915	$231.89	$231.90	$231.90
Purchase #3	$107.66	11.574%	$120.1206	$120.12	$120.10	$120.10
Purchase #4	$173.33	4.198%	$180.6064	$180.61	$180.60	$180.60
Purchase #5	$226.72	12.128%	$254.2166	$254.22	$254.20	$254.20
Purchase #6	$47.46	5.353%	$50.0005	$50.00	$50.00	$50.00
Purchase #7	$53.45	11.492%	$59.5925	$59.59	$59.60	$59.60
7 purchase totals =	$981.86		$1,082.1749	$1,082.18	$1,082.15	$1,082.10