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	$148.85	13.362%	$168.7393	$168.74	$168.75	$168.70
Purchase #2	$204.28	8.827%	$222.3118	$222.31	$222.30	$222.30
Purchase #3	$142.75	12.655%	$160.815	$160.82	$160.80	$160.80
Purchase #4	$154.27	4.334%	$160.9561	$160.96	$160.95	$161.00
Purchase #5	$205.57	12.509%	$231.2848	$231.28	$231.30	$231.30
Purchase #6	$148.63	10.500%	$164.2362	$164.24	$164.25	$164.20
Purchase #7	$65.96	10.163%	$72.6635	$72.66	$72.65	$72.70
7 purchase totals =	$1,070.31		$1,181.0067	$1,181.01	$1,181.00	$1,181.00