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	$82.64	7.735%	$89.0322	$89.03	$89.05	$89.00
Purchase #2	$65.27	7.715%	$70.3056	$70.31	$70.30	$70.30
Purchase #3	$23.52	12.365%	$26.4282	$26.43	$26.45	$26.40
Purchase #4	$69.26	3.709%	$71.8289	$71.83	$71.85	$71.80
Purchase #5	$170.27	7.226%	$182.5737	$182.57	$182.55	$182.60
Purchase #6	$135.44	3.700%	$140.4513	$140.45	$140.45	$140.50
Purchase #7	$166.96	11.145%	$185.5677	$185.57	$185.55	$185.60
7 purchase totals =	$713.36		$766.1876	$766.19	$766.20	$766.20