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	$74.83	3.810%	$77.681	$77.68	$77.70	$77.70
Purchase #2	$187.65	6.859%	$200.5209	$200.52	$200.50	$200.50
Purchase #3	$160.49	12.755%	$180.9605	$180.96	$180.95	$181.00
Purchase #4	$238.50	6.274%	$253.4635	$253.46	$253.45	$253.50
Purchase #5	$26.93	6.623%	$28.7136	$28.71	$28.70	$28.70
Purchase #6	$225.38	5.704%	$238.2357	$238.24	$238.25	$238.20
Purchase #7	$91.53	11.342%	$101.9113	$101.91	$101.90	$101.90
7 purchase totals =	$1,005.31		$1,081.4865	$1,081.48	$1,081.45	$1,081.50