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	$185.35	10.778%	$205.327	$205.33	$205.35	$205.30
Purchase #2	$221.39	10.403%	$244.4212	$244.42	$244.40	$244.40
Purchase #3	$145.45	13.621%	$165.2617	$165.26	$165.25	$165.30
Purchase #4	$99.38	10.210%	$109.5267	$109.53	$109.55	$109.50
Purchase #5	$92.84	9.698%	$101.8436	$101.84	$101.85	$101.80
Purchase #6	$128.91	9.499%	$141.1552	$141.16	$141.15	$141.20
Purchase #7	$95.80	4.608%	$100.2145	$100.21	$100.20	$100.20
7 purchase totals =	$969.12		$1,067.7499	$1,067.75	$1,067.75	$1,067.70