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	$152.50	7.629%	$164.1342	$164.13	$164.15	$164.10
Purchase #2	$53.92	9.443%	$59.0117	$59.01	$59.00	$59.00
Purchase #3	$30.29	3.265%	$31.279	$31.28	$31.30	$31.30
Purchase #4	$43.87	6.664%	$46.7935	$46.79	$46.80	$46.80
Purchase #5	$167.71	8.758%	$182.398	$182.40	$182.40	$182.40
Purchase #6	$88.58	5.872%	$93.7814	$93.78	$93.80	$93.80
Purchase #7	$167.43	3.557%	$173.3855	$173.39	$173.40	$173.40
7 purchase totals =	$704.30		$750.7833	$750.78	$750.85	$750.80