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	$82.57	8.251%	$89.3829	$89.38	$89.40	$89.40
Purchase #2	$42.80	8.531%	$46.4513	$46.45	$46.45	$46.50
Purchase #3	$58.52	10.465%	$64.6441	$64.64	$64.65	$64.60
Purchase #4	$99.72	13.383%	$113.0655	$113.07	$113.05	$113.10
Purchase #5	$210.54	8.655%	$228.7622	$228.76	$228.75	$228.80
Purchase #6	$78.66	8.500%	$85.3461	$85.35	$85.35	$85.30
Purchase #7	$127.89	6.743%	$136.5136	$136.51	$136.50	$136.50
7 purchase totals =	$700.70		$764.1657	$764.16	$764.15	$764.20