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	$148.46	9.685%	$162.8384	$162.84	$162.85	$162.80
Purchase #2	$98.73	5.405%	$104.0664	$104.07	$104.05	$104.10
Purchase #3	$223.97	11.680%	$250.1297	$250.13	$250.15	$250.10
Purchase #4	$98.42	6.578%	$104.8941	$104.89	$104.90	$104.90
Purchase #5	$105.68	10.776%	$117.0681	$117.07	$117.05	$117.10
Purchase #6	$92.72	13.119%	$104.8839	$104.88	$104.90	$104.90
Purchase #7	$240.70	5.601%	$254.1816	$254.18	$254.20	$254.20
7 purchase totals =	$1,008.68		$1,098.0622	$1,098.06	$1,098.10	$1,098.10