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	$147.37	3.635%	$152.7269	$152.73	$152.75	$152.70
Purchase #2	$226.77	6.213%	$240.8592	$240.86	$240.85	$240.90
Purchase #3	$88.45	13.213%	$100.1369	$100.14	$100.15	$100.10
Purchase #4	$195.94	11.334%	$218.1478	$218.15	$218.15	$218.10
Purchase #5	$233.93	13.307%	$265.0591	$265.06	$265.05	$265.10
Purchase #6	$28.77	12.568%	$32.3858	$32.39	$32.40	$32.40
Purchase #7	$69.77	8.264%	$75.5358	$75.54	$75.55	$75.50
7 purchase totals =	$991.00		$1,084.8515	$1,084.87	$1,084.90	$1,084.80