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	$175.63	3.383%	$181.5716	$181.57	$181.55	$181.60
Purchase #2	$247.59	6.783%	$264.384	$264.38	$264.40	$264.40
Purchase #3	$84.78	6.680%	$90.4433	$90.44	$90.45	$90.40
Purchase #4	$109.38	10.486%	$120.8496	$120.85	$120.85	$120.80
Purchase #5	$190.70	11.189%	$212.0374	$212.04	$212.05	$212.00
Purchase #6	$67.26	5.710%	$71.1005	$71.10	$71.10	$71.10
Purchase #7	$239.81	12.640%	$270.122	$270.12	$270.10	$270.10
7 purchase totals =	$1,115.15		$1,210.5084	$1,210.50	$1,210.50	$1,210.40