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	$65.70	9.524%	$71.9573	$71.96	$71.95	$72.00
Purchase #2	$52.82	4.417%	$55.1531	$55.15	$55.15	$55.20
Purchase #3	$184.82	3.314%	$190.9449	$190.94	$190.95	$190.90
Purchase #4	$37.56	9.450%	$41.1094	$41.11	$41.10	$41.10
Purchase #5	$167.46	10.755%	$185.4703	$185.47	$185.45	$185.50
Purchase #6	$119.77	4.801%	$125.5202	$125.52	$125.50	$125.50
Purchase #7	$187.48	10.712%	$207.5629	$207.56	$207.55	$207.60
7 purchase totals =	$815.61		$877.7181	$877.71	$877.65	$877.80