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	$220.55	6.469%	$234.8174	$234.82	$234.80	$234.80
Purchase #2	$170.91	13.632%	$194.2085	$194.21	$194.20	$194.20
Purchase #3	$69.39	4.640%	$72.6097	$72.61	$72.60	$72.60
Purchase #4	$132.83	6.362%	$141.2806	$141.28	$141.30	$141.30
Purchase #5	$168.25	6.307%	$178.8615	$178.86	$178.85	$178.90
Purchase #6	$157.89	12.773%	$178.0573	$178.06	$178.05	$178.10
Purchase #7	$89.61	5.198%	$94.2679	$94.27	$94.25	$94.30
7 purchase totals =	$1,009.43		$1,094.1029	$1,094.11	$1,094.05	$1,094.20