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	$204.89	13.856%	$233.2796	$233.28	$233.30	$233.30
Purchase #2	$147.55	6.842%	$157.6454	$157.65	$157.65	$157.60
Purchase #3	$86.38	8.836%	$94.0125	$94.01	$94.00	$94.00
Purchase #4	$135.61	7.109%	$145.2505	$145.25	$145.25	$145.30
Purchase #5	$188.95	8.432%	$204.8823	$204.88	$204.90	$204.90
Purchase #6	$123.42	8.479%	$133.8848	$133.88	$133.90	$133.90
Purchase #7	$121.43	8.386%	$131.6131	$131.61	$131.60	$131.60
7 purchase totals =	$1,008.23		$1,100.5682	$1,100.56	$1,100.60	$1,100.60