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	$153.46	4.359%	$160.1493	$160.15	$160.15	$160.10
Purchase #2	$165.84	11.872%	$185.5285	$185.53	$185.55	$185.50
Purchase #3	$140.59	5.651%	$148.5347	$148.53	$148.55	$148.50
Purchase #4	$37.87	13.202%	$42.8696	$42.87	$42.85	$42.90
Purchase #5	$180.88	8.656%	$196.537	$196.54	$196.55	$196.50
Purchase #6	$167.75	7.803%	$180.8395	$180.84	$180.85	$180.80
Purchase #7	$177.56	3.653%	$184.0463	$184.05	$184.05	$184.00
7 purchase totals =	$1,023.95		$1,098.5049	$1,098.51	$1,098.55	$1,098.30