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	$140.64	7.183%	$150.7422	$150.74	$150.75	$150.70
Purchase #2	$42.43	8.154%	$45.8897	$45.89	$45.90	$45.90
Purchase #3	$247.96	9.519%	$271.5633	$271.56	$271.55	$271.60
Purchase #4	$185.94	5.561%	$196.2801	$196.28	$196.30	$196.30
Purchase #5	$191.32	12.501%	$215.2369	$215.24	$215.25	$215.20
Purchase #6	$164.84	10.309%	$181.8334	$181.83	$181.85	$181.80
Purchase #7	$83.51	3.222%	$86.2007	$86.20	$86.20	$86.20
7 purchase totals =	$1,056.64		$1,147.7463	$1,147.74	$1,147.80	$1,147.70