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	$66.28	4.560%	$69.3024	$69.30	$69.30	$69.30
Purchase #2	$129.63	8.239%	$140.3102	$140.31	$140.30	$140.30
Purchase #3	$31.86	11.432%	$35.5022	$35.50	$35.50	$35.50
Purchase #4	$119.43	6.372%	$127.0401	$127.04	$127.05	$127.00
Purchase #5	$101.75	11.440%	$113.3902	$113.39	$113.40	$113.40
Purchase #6	$107.89	11.118%	$119.8852	$119.89	$119.90	$119.90
Purchase #7	$19.92	4.438%	$20.804	$20.80	$20.80	$20.80
7 purchase totals =	$576.76		$626.2343	$626.23	$626.25	$626.20