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	$177.90	13.317%	$201.5909	$201.59	$201.60	$201.60
Purchase #2	$158.88	12.841%	$179.2818	$179.28	$179.30	$179.30
Purchase #3	$74.43	11.563%	$83.0363	$83.04	$83.05	$83.00
Purchase #4	$209.80	11.516%	$233.9606	$233.96	$233.95	$234.00
Purchase #5	$74.66	11.793%	$83.4647	$83.46	$83.45	$83.50
Purchase #6	$91.28	11.855%	$102.1012	$102.10	$102.10	$102.10
Purchase #7	$71.56	9.430%	$78.3081	$78.31	$78.30	$78.30
7 purchase totals =	$858.51		$961.7436	$961.74	$961.75	$961.80