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	$160.72	13.774%	$182.8576	$182.86	$182.85	$182.90
Purchase #2	$236.37	13.869%	$269.1522	$269.15	$269.15	$269.20
Purchase #3	$9.35	7.310%	$10.0335	$10.03	$10.05	$10.00
Purchase #4	$243.88	12.274%	$273.8138	$273.81	$273.80	$273.80
Purchase #5	$175.30	9.476%	$191.9114	$191.91	$191.90	$191.90
Purchase #6	$67.27	13.718%	$76.4981	$76.50	$76.50	$76.50
Purchase #7	$86.85	5.219%	$91.3827	$91.38	$91.40	$91.40
7 purchase totals =	$979.74		$1,095.6493	$1,095.64	$1,095.65	$1,095.70