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	$83.72	12.794%	$94.4311	$94.43	$94.45	$94.40
Purchase #2	$126.79	12.262%	$142.337	$142.34	$142.35	$142.30
Purchase #3	$61.71	3.132%	$63.6428	$63.64	$63.65	$63.60
Purchase #4	$210.41	6.603%	$224.3034	$224.30	$224.30	$224.30
Purchase #5	$91.91	5.112%	$96.6084	$96.61	$96.60	$96.60
Purchase #6	$177.34	11.768%	$198.2094	$198.21	$198.20	$198.20
Purchase #7	$250.29	12.401%	$281.3285	$281.33	$281.35	$281.30
7 purchase totals =	$1,002.17		$1,100.8606	$1,100.86	$1,100.90	$1,100.70