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	$215.64	9.160%	$235.3926	$235.39	$235.40	$235.40
Purchase #2	$79.84	3.664%	$82.7653	$82.77	$82.75	$82.80
Purchase #3	$249.31	10.465%	$275.4003	$275.40	$275.40	$275.40
Purchase #4	$129.61	6.731%	$138.334	$138.33	$138.35	$138.30
Purchase #5	$7.47	4.491%	$7.8055	$7.81	$7.80	$7.80
Purchase #6	$100.37	3.190%	$103.5718	$103.57	$103.55	$103.60
Purchase #7	$96.41	7.355%	$103.501	$103.50	$103.50	$103.50
7 purchase totals =	$878.65		$946.7705	$946.77	$946.75	$946.80