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	$54.43	4.415%	$56.8331	$56.83	$56.85	$56.80
Purchase #2	$82.89	10.834%	$91.8703	$91.87	$91.85	$91.90
Purchase #3	$139.75	6.355%	$148.6311	$148.63	$148.65	$148.60
Purchase #4	$116.32	10.827%	$128.914	$128.91	$128.90	$128.90
Purchase #5	$219.84	6.137%	$233.3316	$233.33	$233.35	$233.30
Purchase #6	$150.65	13.233%	$170.5855	$170.59	$170.60	$170.60
Purchase #7	$242.29	8.552%	$263.0106	$263.01	$263.00	$263.00
7 purchase totals =	$1,006.17		$1,093.1762	$1,093.17	$1,093.20	$1,093.10