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	$194.25	5.326%	$204.5958	$204.60	$204.60	$204.60
Purchase #2	$62.83	7.372%	$67.4618	$67.46	$67.45	$67.50
Purchase #3	$19.80	9.251%	$21.6317	$21.63	$21.65	$21.60
Purchase #4	$173.33	10.436%	$191.4187	$191.42	$191.40	$191.40
Purchase #5	$93.64	7.694%	$100.8447	$100.84	$100.85	$100.80
Purchase #6	$28.87	7.779%	$31.1158	$31.12	$31.10	$31.10
Purchase #7	$127.88	12.399%	$143.7358	$143.74	$143.75	$143.70
7 purchase totals =	$700.60		$760.8043	$760.81	$760.80	$760.70