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	$88.40	9.497%	$96.7953	$96.80	$96.80	$96.80
Purchase #2	$41.49	4.743%	$43.4579	$43.46	$43.45	$43.50
Purchase #3	$72.79	11.114%	$80.8799	$80.88	$80.90	$80.90
Purchase #4	$85.36	11.453%	$95.1363	$95.14	$95.15	$95.10
Purchase #5	$168.73	11.636%	$188.3634	$188.36	$188.35	$188.40
Purchase #6	$196.90	10.849%	$218.2617	$218.26	$218.25	$218.30
Purchase #7	$13.85	6.777%	$14.7886	$14.79	$14.80	$14.80
7 purchase totals =	$667.52		$737.6831	$737.69	$737.70	$737.80