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	$74.29	10.681%	$82.2249	$82.22	$82.20	$82.20
Purchase #2	$144.50	8.508%	$156.7941	$156.79	$156.80	$156.80
Purchase #3	$154.51	6.459%	$164.4898	$164.49	$164.50	$164.50
Purchase #4	$159.69	6.395%	$169.9022	$169.90	$169.90	$169.90
Purchase #5	$227.88	12.730%	$256.8891	$256.89	$256.90	$256.90
Purchase #6	$70.35	13.373%	$79.7579	$79.76	$79.75	$79.80
Purchase #7	$169.93	8.657%	$184.6408	$184.64	$184.65	$184.60
7 purchase totals =	$1,001.15		$1,094.6988	$1,094.69	$1,094.70	$1,094.70