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	$82.52	8.162%	$89.2553	$89.26	$89.25	$89.30
Purchase #2	$133.88	12.638%	$150.7998	$150.80	$150.80	$150.80
Purchase #3	$56.56	6.630%	$60.3099	$60.31	$60.30	$60.30
Purchase #4	$173.55	10.448%	$191.6825	$191.68	$191.70	$191.70
Purchase #5	$225.69	5.479%	$238.0556	$238.06	$238.05	$238.10
Purchase #6	$227.67	7.545%	$244.8477	$244.85	$244.85	$244.80
Purchase #7	$96.46	10.342%	$106.4359	$106.44	$106.45	$106.40
7 purchase totals =	$996.33		$1,081.3867	$1,081.40	$1,081.40	$1,081.40