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	$108.41	11.556%	$120.9379	$120.94	$120.95	$120.90
Purchase #2	$151.70	13.549%	$172.2538	$172.25	$172.25	$172.30
Purchase #3	$24.49	11.483%	$27.3022	$27.30	$27.30	$27.30
Purchase #4	$100.63	10.150%	$110.8439	$110.84	$110.85	$110.80
Purchase #5	$119.43	8.333%	$129.3821	$129.38	$129.40	$129.40
Purchase #6	$164.88	13.105%	$186.4875	$186.49	$186.50	$186.50
Purchase #7	$41.68	8.681%	$45.2982	$45.30	$45.30	$45.30
7 purchase totals =	$711.22		$792.5056	$792.50	$792.55	$792.50