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	$214.44	9.142%	$234.0441	$234.04	$234.05	$234.00
Purchase #2	$157.54	6.369%	$167.5737	$167.57	$167.55	$167.60
Purchase #3	$82.71	4.693%	$86.5916	$86.59	$86.60	$86.60
Purchase #4	$173.25	6.102%	$183.8217	$183.82	$183.80	$183.80
Purchase #5	$35.82	13.781%	$40.7564	$40.76	$40.75	$40.80
Purchase #6	$158.72	5.728%	$167.8115	$167.81	$167.80	$167.80
Purchase #7	$152.40	8.474%	$165.3144	$165.31	$165.30	$165.30
7 purchase totals =	$974.88		$1,045.9134	$1,045.90	$1,045.85	$1,045.90