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	$184.31	11.174%	$204.9048	$204.90	$204.90	$204.90
Purchase #2	$125.86	13.845%	$143.2853	$143.29	$143.30	$143.30
Purchase #3	$56.49	12.198%	$63.3807	$63.38	$63.40	$63.40
Purchase #4	$99.78	13.546%	$113.2962	$113.30	$113.30	$113.30
Purchase #5	$228.36	13.341%	$258.8255	$258.83	$258.85	$258.80
Purchase #6	$170.57	6.405%	$181.495	$181.50	$181.50	$181.50
Purchase #7	$160.32	13.618%	$182.1524	$182.15	$182.15	$182.20
7 purchase totals =	$1,025.69		$1,147.3399	$1,147.35	$1,147.40	$1,147.40