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	$169.57	7.834%	$182.8541	$182.85	$182.85	$182.90
Purchase #2	$30.32	11.324%	$33.7534	$33.75	$33.75	$33.80
Purchase #3	$34.89	7.679%	$37.5692	$37.57	$37.55	$37.60
Purchase #4	$70.79	13.179%	$80.1194	$80.12	$80.10	$80.10
Purchase #5	$96.56	10.568%	$106.7645	$106.76	$106.75	$106.80
Purchase #6	$94.54	7.318%	$101.4584	$101.46	$101.45	$101.50
Purchase #7	$109.84	12.124%	$123.157	$123.16	$123.15	$123.20
7 purchase totals =	$606.51		$665.6760	$665.67	$665.60	$665.90