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	$233.92	4.867%	$245.3049	$245.30	$245.30	$245.30
Purchase #2	$212.74	7.865%	$229.472	$229.47	$229.45	$229.50
Purchase #3	$46.98	12.725%	$52.9582	$52.96	$52.95	$53.00
Purchase #4	$17.32	13.104%	$19.5896	$19.59	$19.60	$19.60
Purchase #5	$204.44	10.326%	$225.5505	$225.55	$225.55	$225.60
Purchase #6	$81.32	12.568%	$91.5403	$91.54	$91.55	$91.50
Purchase #7	$125.82	9.116%	$137.2898	$137.29	$137.30	$137.30
7 purchase totals =	$922.54		$1,001.7053	$1,001.70	$1,001.70	$1,001.80