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	$183.93	6.789%	$196.417	$196.42	$196.40	$196.40
Purchase #2	$82.38	3.829%	$85.5343	$85.53	$85.55	$85.50
Purchase #3	$239.91	7.581%	$258.0976	$258.10	$258.10	$258.10
Purchase #4	$233.27	4.561%	$243.9094	$243.91	$243.90	$243.90
Purchase #5	$120.49	8.404%	$130.616	$130.62	$130.60	$130.60
Purchase #6	$83.78	4.606%	$87.6389	$87.64	$87.65	$87.60
Purchase #7	$40.65	12.148%	$45.5882	$45.59	$45.60	$45.60
7 purchase totals =	$984.41		$1,047.8014	$1,047.81	$1,047.80	$1,047.70