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	$207.35	8.715%	$225.4206	$225.42	$225.40	$225.40
Purchase #2	$202.92	5.229%	$213.5307	$213.53	$213.55	$213.50
Purchase #3	$20.88	9.495%	$22.8626	$22.86	$22.85	$22.90
Purchase #4	$43.42	4.431%	$45.3439	$45.34	$45.35	$45.30
Purchase #5	$122.37	4.209%	$127.5206	$127.52	$127.50	$127.50
Purchase #6	$47.62	11.559%	$53.1244	$53.12	$53.10	$53.10
Purchase #7	$91.90	5.634%	$97.0776	$97.08	$97.10	$97.10
7 purchase totals =	$736.46		$784.8804	$784.87	$784.85	$784.80