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	$137.58	9.513%	$150.668	$150.67	$150.65	$150.70
Purchase #2	$196.64	11.658%	$219.5643	$219.56	$219.55	$219.60
Purchase #3	$93.46	11.517%	$104.2238	$104.22	$104.20	$104.20
Purchase #4	$222.65	10.139%	$245.2245	$245.22	$245.20	$245.20
Purchase #5	$157.84	6.458%	$168.0333	$168.03	$168.05	$168.00
Purchase #6	$59.76	13.513%	$67.8354	$67.84	$67.85	$67.80
Purchase #7	$79.95	8.668%	$86.8801	$86.88	$86.90	$86.90
7 purchase totals =	$947.88		$1,042.4294	$1,042.42	$1,042.40	$1,042.40