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	$72.92	3.578%	$75.5291	$75.53	$75.55	$75.50
Purchase #2	$47.94	7.345%	$51.4612	$51.46	$51.45	$51.50
Purchase #3	$42.67	13.694%	$48.5132	$48.51	$48.50	$48.50
Purchase #4	$218.48	9.114%	$238.3923	$238.39	$238.40	$238.40
Purchase #5	$206.91	13.354%	$234.5408	$234.54	$234.55	$234.50
Purchase #6	$129.68	12.709%	$146.161	$146.16	$146.15	$146.20
Purchase #7	$225.45	8.166%	$243.8602	$243.86	$243.85	$243.90
7 purchase totals =	$944.05		$1,038.4578	$1,038.45	$1,038.45	$1,038.50