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	$188.62	9.385%	$206.322	$206.32	$206.30	$206.30
Purchase #2	$54.31	4.739%	$56.8838	$56.88	$56.90	$56.90
Purchase #3	$34.92	7.530%	$37.5495	$37.55	$37.55	$37.50
Purchase #4	$30.68	7.297%	$32.9187	$32.92	$32.90	$32.90
Purchase #5	$122.81	6.790%	$131.1488	$131.15	$131.15	$131.10
Purchase #6	$84.85	8.800%	$92.3168	$92.32	$92.30	$92.30
Purchase #7	$38.69	13.259%	$43.8199	$43.82	$43.80	$43.80
7 purchase totals =	$554.88		$600.9595	$600.96	$600.90	$600.80