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	$184.84	12.479%	$207.9062	$207.91	$207.90	$207.90
Purchase #2	$8.47	4.487%	$8.85	$8.85	$8.85	$8.90
Purchase #3	$18.78	9.518%	$20.5675	$20.57	$20.55	$20.60
Purchase #4	$43.40	3.850%	$45.0709	$45.07	$45.05	$45.10
Purchase #5	$85.91	6.673%	$91.6428	$91.64	$91.65	$91.60
Purchase #6	$123.79	3.194%	$127.7439	$127.74	$127.75	$127.70
Purchase #7	$65.90	10.310%	$72.6943	$72.69	$72.70	$72.70
7 purchase totals =	$531.09		$574.4756	$574.47	$574.45	$574.50