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	$183.53	11.593%	$204.8066	$204.81	$204.80	$204.80
Purchase #2	$229.34	5.464%	$241.8711	$241.87	$241.85	$241.90
Purchase #3	$166.45	7.423%	$178.8056	$178.81	$178.80	$178.80
Purchase #4	$229.68	7.565%	$247.0553	$247.06	$247.05	$247.10
Purchase #5	$31.56	13.755%	$35.9011	$35.90	$35.90	$35.90
Purchase #6	$73.48	6.497%	$78.254	$78.25	$78.25	$78.30
Purchase #7	$103.85	12.390%	$116.717	$116.72	$116.70	$116.70
7 purchase totals =	$1,017.89		$1,103.4107	$1,103.42	$1,103.35	$1,103.50