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	$108.82	13.665%	$123.6903	$123.69	$123.70	$123.70
Purchase #2	$207.70	13.223%	$235.1642	$235.16	$235.15	$235.20
Purchase #3	$195.92	4.444%	$204.6267	$204.63	$204.65	$204.60
Purchase #4	$196.42	6.315%	$208.8239	$208.82	$208.80	$208.80
Purchase #5	$84.73	5.688%	$89.5494	$89.55	$89.55	$89.50
Purchase #6	$173.95	8.241%	$188.2852	$188.29	$188.30	$188.30
Purchase #7	$94.81	5.507%	$100.0312	$100.03	$100.05	$100.00
7 purchase totals =	$1,062.35		$1,150.1709	$1,150.17	$1,150.20	$1,150.10