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	$214.64	6.848%	$229.3385	$229.34	$229.35	$229.30
Purchase #2	$249.85	8.197%	$270.3302	$270.33	$270.35	$270.30
Purchase #3	$194.91	12.700%	$219.6636	$219.66	$219.65	$219.70
Purchase #4	$139.77	12.196%	$156.8163	$156.82	$156.80	$156.80
Purchase #5	$96.98	9.222%	$105.9235	$105.92	$105.90	$105.90
Purchase #6	$175.62	9.107%	$191.6137	$191.61	$191.60	$191.60
Purchase #7	$216.33	7.204%	$231.9144	$231.91	$231.90	$231.90
7 purchase totals =	$1,288.10		$1,405.6002	$1,405.59	$1,405.55	$1,405.50