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	$63.59	11.819%	$71.1057	$71.11	$71.10	$71.10
Purchase #2	$225.55	7.771%	$243.0775	$243.08	$243.10	$243.10
Purchase #3	$24.96	13.365%	$28.2959	$28.30	$28.30	$28.30
Purchase #4	$73.44	13.112%	$83.0695	$83.07	$83.05	$83.10
Purchase #5	$216.50	4.312%	$225.8355	$225.84	$225.85	$225.80
Purchase #6	$114.63	12.374%	$128.8143	$128.81	$128.80	$128.80
Purchase #7	$208.86	12.675%	$235.333	$235.33	$235.35	$235.30
7 purchase totals =	$927.53		$1,015.5314	$1,015.54	$1,015.55	$1,015.50