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	$178.42	9.151%	$194.7472	$194.75	$194.75	$194.70
Purchase #2	$238.50	9.805%	$261.8849	$261.88	$261.90	$261.90
Purchase #3	$222.74	4.841%	$233.5228	$233.52	$233.50	$233.50
Purchase #4	$228.76	6.261%	$243.0827	$243.08	$243.10	$243.10
Purchase #5	$250.82	7.153%	$268.7612	$268.76	$268.75	$268.80
Purchase #6	$27.43	12.404%	$30.8324	$30.83	$30.85	$30.80
Purchase #7	$92.91	8.436%	$100.7479	$100.75	$100.75	$100.70
7 purchase totals =	$1,239.58		$1,333.5791	$1,333.57	$1,333.60	$1,333.50