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	$170.32	7.300%	$182.7534	$182.75	$182.75	$182.80
Purchase #2	$64.32	13.572%	$73.0495	$73.05	$73.05	$73.00
Purchase #3	$89.96	3.264%	$92.8963	$92.90	$92.90	$92.90
Purchase #4	$69.83	12.242%	$78.3786	$78.38	$78.40	$78.40
Purchase #5	$220.76	12.441%	$248.2248	$248.22	$248.20	$248.20
Purchase #6	$73.64	4.737%	$77.1283	$77.13	$77.15	$77.10
Purchase #7	$139.48	7.654%	$150.1558	$150.16	$150.15	$150.20
7 purchase totals =	$828.31		$902.5867	$902.59	$902.60	$902.60