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	$148.86	12.771%	$167.8709	$167.87	$167.85	$167.90
Purchase #2	$228.76	3.360%	$236.4463	$236.45	$236.45	$236.40
Purchase #3	$90.96	5.634%	$96.0847	$96.08	$96.10	$96.10
Purchase #4	$249.31	10.111%	$274.5177	$274.52	$274.50	$274.50
Purchase #5	$244.73	11.717%	$273.405	$273.41	$273.40	$273.40
Purchase #6	$72.37	10.616%	$80.0528	$80.05	$80.05	$80.10
Purchase #7	$140.44	7.619%	$151.1401	$151.14	$151.15	$151.10
7 purchase totals =	$1,175.43		$1,279.5175	$1,279.52	$1,279.50	$1,279.50