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	$91.44	4.116%	$95.2037	$95.20	$95.20	$95.20
Purchase #2	$57.71	4.268%	$60.1731	$60.17	$60.15	$60.20
Purchase #3	$66.41	10.465%	$73.3598	$73.36	$73.35	$73.40
Purchase #4	$56.79	5.506%	$59.9169	$59.92	$59.90	$59.90
Purchase #5	$164.29	5.467%	$173.2717	$173.27	$173.25	$173.30
Purchase #6	$47.76	9.440%	$52.2685	$52.27	$52.25	$52.30
Purchase #7	$121.28	12.366%	$136.2775	$136.28	$136.30	$136.30
7 purchase totals =	$605.68		$650.4712	$650.47	$650.40	$650.60