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	$131.27	3.651%	$136.0627	$136.06	$136.05	$136.10
Purchase #2	$175.96	11.808%	$196.7374	$196.74	$196.75	$196.70
Purchase #3	$148.82	4.138%	$154.9782	$154.98	$155.00	$155.00
Purchase #4	$247.38	6.816%	$264.2414	$264.24	$264.25	$264.20
Purchase #5	$62.34	7.321%	$66.9039	$66.90	$66.90	$66.90
Purchase #6	$171.51	11.481%	$191.2011	$191.20	$191.20	$191.20
Purchase #7	$63.61	5.791%	$67.2937	$67.29	$67.30	$67.30
7 purchase totals =	$1,000.89		$1,077.4184	$1,077.41	$1,077.45	$1,077.40