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	$65.76	11.433%	$73.2783	$73.28	$73.30	$73.30
Purchase #2	$121.73	4.812%	$127.5876	$127.59	$127.60	$127.60
Purchase #3	$35.91	12.264%	$40.314	$40.31	$40.30	$40.30
Purchase #4	$141.41	3.736%	$146.6931	$146.69	$146.70	$146.70
Purchase #5	$167.84	11.327%	$186.8512	$186.85	$186.85	$186.90
Purchase #6	$158.87	7.242%	$170.3754	$170.38	$170.40	$170.40
Purchase #7	$223.25	5.865%	$236.3436	$236.34	$236.35	$236.30
7 purchase totals =	$914.77		$981.4432	$981.44	$981.50	$981.50