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	$99.37	4.366%	$103.7085	$103.71	$103.70	$103.70
Purchase #2	$211.90	7.510%	$227.8137	$227.81	$227.80	$227.80
Purchase #3	$241.52	3.121%	$249.0578	$249.06	$249.05	$249.10
Purchase #4	$47.56	13.803%	$54.1247	$54.12	$54.10	$54.10
Purchase #5	$146.50	3.627%	$151.8136	$151.81	$151.80	$151.80
Purchase #6	$245.79	11.222%	$273.3726	$273.37	$273.35	$273.40
Purchase #7	$41.70	6.755%	$44.5168	$44.52	$44.50	$44.50
7 purchase totals =	$1,034.34		$1,104.4077	$1,104.40	$1,104.30	$1,104.40