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	$66.44	9.796%	$72.9485	$72.95	$72.95	$72.90
Purchase #2	$42.82	7.642%	$46.0923	$46.09	$46.10	$46.10
Purchase #3	$86.76	7.357%	$93.1429	$93.14	$93.15	$93.10
Purchase #4	$48.30	10.424%	$53.3348	$53.33	$53.35	$53.30
Purchase #5	$96.61	6.436%	$102.8278	$102.83	$102.85	$102.80
Purchase #6	$205.43	6.774%	$219.3458	$219.35	$219.35	$219.30
Purchase #7	$56.76	10.135%	$62.5126	$62.51	$62.50	$62.50
7 purchase totals =	$603.12		$650.2047	$650.20	$650.25	$650.00