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	$198.73	11.757%	$222.0947	$222.09	$222.10	$222.10
Purchase #2	$53.79	10.722%	$59.5574	$59.56	$59.55	$59.60
Purchase #3	$96.82	6.357%	$102.9748	$102.97	$102.95	$103.00
Purchase #4	$57.53	4.128%	$59.9048	$59.90	$59.90	$59.90
Purchase #5	$159.55	9.563%	$174.8078	$174.81	$174.80	$174.80
Purchase #6	$96.51	11.226%	$107.3442	$107.34	$107.35	$107.30
Purchase #7	$24.74	8.829%	$26.9243	$26.92	$26.90	$26.90
7 purchase totals =	$687.67		$753.6080	$753.59	$753.55	$753.60