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	$67.92	13.458%	$77.0607	$77.06	$77.05	$77.10
Purchase #2	$58.73	12.812%	$66.2545	$66.25	$66.25	$66.30
Purchase #3	$118.75	3.853%	$123.3254	$123.33	$123.35	$123.30
Purchase #4	$5.92	12.816%	$6.6787	$6.68	$6.70	$6.70
Purchase #5	$85.40	13.299%	$96.7573	$96.76	$96.75	$96.80
Purchase #6	$100.66	10.610%	$111.34	$111.34	$111.35	$111.30
Purchase #7	$204.69	6.837%	$218.6847	$218.68	$218.70	$218.70
7 purchase totals =	$642.07		$700.1013	$700.10	$700.15	$700.20