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	$237.68	3.662%	$246.3838	$246.38	$246.40	$246.40
Purchase #2	$75.39	13.128%	$85.2872	$85.29	$85.30	$85.30
Purchase #3	$90.36	6.813%	$96.5162	$96.52	$96.50	$96.50
Purchase #4	$208.76	11.776%	$233.3436	$233.34	$233.35	$233.30
Purchase #5	$29.37	3.592%	$30.425	$30.43	$30.45	$30.40
Purchase #6	$162.91	5.106%	$171.2282	$171.23	$171.25	$171.20
Purchase #7	$127.71	8.745%	$138.8782	$138.88	$138.90	$138.90
7 purchase totals =	$932.18		$1,002.0622	$1,002.07	$1,002.15	$1,002.00