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	$197.77	13.236%	$223.9468	$223.95	$223.95	$223.90
Purchase #2	$79.43	13.268%	$89.9688	$89.97	$89.95	$90.00
Purchase #3	$25.28	7.529%	$27.1833	$27.18	$27.20	$27.20
Purchase #4	$219.83	6.352%	$233.7936	$233.79	$233.80	$233.80
Purchase #5	$29.94	9.474%	$32.7765	$32.78	$32.80	$32.80
Purchase #6	$140.32	7.169%	$150.3795	$150.38	$150.40	$150.40
Purchase #7	$64.35	4.631%	$67.33	$67.33	$67.35	$67.30
7 purchase totals =	$756.92		$825.3785	$825.38	$825.45	$825.40