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	$215.84	6.304%	$229.4466	$229.45	$229.45	$229.40
Purchase #2	$77.44	6.501%	$82.4744	$82.47	$82.45	$82.50
Purchase #3	$188.44	9.206%	$205.7878	$205.79	$205.80	$205.80
Purchase #4	$133.30	6.183%	$141.5419	$141.54	$141.55	$141.50
Purchase #5	$230.50	10.156%	$253.9096	$253.91	$253.90	$253.90
Purchase #6	$90.75	5.770%	$95.9863	$95.99	$96.00	$96.00
Purchase #7	$178.66	10.104%	$196.7118	$196.71	$196.70	$196.70
7 purchase totals =	$1,114.93		$1,205.8584	$1,205.86	$1,205.85	$1,205.80