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	$47.52	11.334%	$52.9059	$52.91	$52.90	$52.90
Purchase #2	$231.61	5.155%	$243.5495	$243.55	$243.55	$243.50
Purchase #3	$208.94	9.204%	$228.1708	$228.17	$228.15	$228.20
Purchase #4	$72.54	9.766%	$79.6243	$79.62	$79.60	$79.60
Purchase #5	$226.38	9.780%	$248.52	$248.52	$248.50	$248.50
Purchase #6	$25.45	11.420%	$28.3564	$28.36	$28.35	$28.40
Purchase #7	$157.29	3.546%	$162.8675	$162.87	$162.85	$162.90
7 purchase totals =	$969.73		$1,043.9944	$1,044.00	$1,043.90	$1,044.00