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	$225.65	10.295%	$248.8807	$248.88	$248.90	$248.90
Purchase #2	$223.39	10.165%	$246.0976	$246.10	$246.10	$246.10
Purchase #3	$55.92	12.866%	$63.1147	$63.11	$63.10	$63.10
Purchase #4	$98.76	5.833%	$104.5207	$104.52	$104.50	$104.50
Purchase #5	$210.65	5.833%	$222.9372	$222.94	$222.95	$222.90
Purchase #6	$137.76	9.831%	$151.3032	$151.30	$151.30	$151.30
Purchase #7	$195.72	13.568%	$222.2753	$222.28	$222.30	$222.30
7 purchase totals =	$1,147.85		$1,259.1294	$1,259.13	$1,259.15	$1,259.10