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	$181.87	6.236%	$193.2114	$193.21	$193.20	$193.20
Purchase #2	$242.56	8.630%	$263.4929	$263.49	$263.50	$263.50
Purchase #3	$200.85	13.758%	$228.4829	$228.48	$228.50	$228.50
Purchase #4	$57.56	11.213%	$64.0142	$64.01	$64.00	$64.00
Purchase #5	$88.37	7.513%	$95.0092	$95.01	$95.00	$95.00
Purchase #6	$90.33	8.651%	$98.1444	$98.14	$98.15	$98.10
Purchase #7	$104.87	6.312%	$111.4894	$111.49	$111.50	$111.50
7 purchase totals =	$966.41		$1,053.8444	$1,053.83	$1,053.85	$1,053.80