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	$177.44	4.377%	$185.2065	$185.21	$185.20	$185.20
Purchase #2	$174.56	8.609%	$189.5879	$189.59	$189.60	$189.60
Purchase #3	$29.90	11.477%	$33.3316	$33.33	$33.35	$33.30
Purchase #4	$147.98	11.813%	$165.4609	$165.46	$165.45	$165.50
Purchase #5	$105.38	6.463%	$112.1907	$112.19	$112.20	$112.20
Purchase #6	$241.37	11.490%	$269.1034	$269.10	$269.10	$269.10
Purchase #7	$171.90	9.513%	$188.2528	$188.25	$188.25	$188.30
7 purchase totals =	$1,048.53		$1,143.1338	$1,143.13	$1,143.15	$1,143.20