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	$96.37	3.297%	$99.5473	$99.55	$99.55	$99.50
Purchase #2	$96.56	5.206%	$101.5869	$101.59	$101.60	$101.60
Purchase #3	$191.40	5.497%	$201.9213	$201.92	$201.90	$201.90
Purchase #4	$248.99	12.297%	$279.6083	$279.61	$279.60	$279.60
Purchase #5	$77.83	6.448%	$82.8485	$82.85	$82.85	$82.80
Purchase #6	$64.98	9.347%	$71.0537	$71.05	$71.05	$71.10
Purchase #7	$183.41	4.741%	$192.1055	$192.11	$192.10	$192.10
7 purchase totals =	$959.54		$1,028.6715	$1,028.68	$1,028.65	$1,028.60