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	$41.93	10.647%	$46.3943	$46.39	$46.40	$46.40
Purchase #2	$124.32	8.636%	$135.0563	$135.06	$135.05	$135.10
Purchase #3	$66.30	9.180%	$72.3863	$72.39	$72.40	$72.40
Purchase #4	$79.61	13.420%	$90.2937	$90.29	$90.30	$90.30
Purchase #5	$209.92	8.716%	$228.2166	$228.22	$228.20	$228.20
Purchase #6	$50.69	11.730%	$56.6359	$56.64	$56.65	$56.60
Purchase #7	$53.95	13.736%	$61.3606	$61.36	$61.35	$61.40
7 purchase totals =	$626.72		$690.3437	$690.35	$690.35	$690.40