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	$193.85	6.668%	$206.7759	$206.78	$206.80	$206.80
Purchase #2	$245.95	5.349%	$259.1059	$259.11	$259.10	$259.10
Purchase #3	$59.50	10.190%	$65.5631	$65.56	$65.55	$65.60
Purchase #4	$140.35	5.161%	$147.5935	$147.59	$147.60	$147.60
Purchase #5	$184.33	3.625%	$191.012	$191.01	$191.00	$191.00
Purchase #6	$148.60	10.784%	$164.625	$164.63	$164.65	$164.60
Purchase #7	$198.66	10.687%	$219.8908	$219.89	$219.90	$219.90
7 purchase totals =	$1,171.24		$1,254.5662	$1,254.57	$1,254.60	$1,254.60