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	$74.46	5.468%	$78.5315	$78.53	$78.55	$78.50
Purchase #2	$86.37	10.355%	$95.3136	$95.31	$95.30	$95.30
Purchase #3	$196.60	12.141%	$220.4692	$220.47	$220.45	$220.50
Purchase #4	$46.78	3.466%	$48.4014	$48.40	$48.40	$48.40
Purchase #5	$59.86	8.346%	$64.8559	$64.86	$64.85	$64.90
Purchase #6	$146.45	4.623%	$153.2204	$153.22	$153.20	$153.20
Purchase #7	$231.59	9.592%	$253.8041	$253.80	$253.80	$253.80
7 purchase totals =	$842.11		$914.5961	$914.59	$914.55	$914.60