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	$219.39	5.302%	$231.0221	$231.02	$231.00	$231.00
Purchase #2	$245.35	7.541%	$263.8518	$263.85	$263.85	$263.90
Purchase #3	$19.39	3.869%	$20.1402	$20.14	$20.15	$20.10
Purchase #4	$181.67	4.642%	$190.1031	$190.10	$190.10	$190.10
Purchase #5	$38.25	4.392%	$39.9299	$39.93	$39.95	$39.90
Purchase #6	$99.99	6.487%	$106.4764	$106.48	$106.50	$106.50
Purchase #7	$69.63	12.465%	$78.3094	$78.31	$78.30	$78.30
7 purchase totals =	$873.67		$929.8329	$929.83	$929.85	$929.80