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	$70.25	10.229%	$77.4359	$77.44	$77.45	$77.40
Purchase #2	$31.50	12.138%	$35.3235	$35.32	$35.30	$35.30
Purchase #3	$97.43	11.479%	$108.614	$108.61	$108.60	$108.60
Purchase #4	$172.71	7.125%	$185.0156	$185.02	$185.00	$185.00
Purchase #5	$104.39	3.571%	$108.1178	$108.12	$108.10	$108.10
Purchase #6	$95.33	12.365%	$107.1176	$107.12	$107.10	$107.10
Purchase #7	$159.70	3.219%	$164.8407	$164.84	$164.85	$164.80
7 purchase totals =	$731.31		$786.4651	$786.47	$786.40	$786.30