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	$35.45	4.865%	$37.1746	$37.17	$37.15	$37.20
Purchase #2	$56.58	10.424%	$62.4779	$62.48	$62.50	$62.50
Purchase #3	$162.80	12.703%	$183.4805	$183.48	$183.50	$183.50
Purchase #4	$101.51	3.574%	$105.138	$105.14	$105.15	$105.10
Purchase #5	$22.43	8.333%	$24.2991	$24.30	$24.30	$24.30
Purchase #6	$38.26	8.583%	$41.5439	$41.54	$41.55	$41.50
Purchase #7	$58.69	4.694%	$61.4449	$61.44	$61.45	$61.40
7 purchase totals =	$475.72		$515.5589	$515.55	$515.60	$515.50