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	$144.81	5.506%	$152.7832	$152.78	$152.80	$152.80
Purchase #2	$185.32	3.379%	$191.582	$191.58	$191.60	$191.60
Purchase #3	$54.84	8.347%	$59.4175	$59.42	$59.40	$59.40
Purchase #4	$220.43	7.649%	$237.2907	$237.29	$237.30	$237.30
Purchase #5	$12.78	5.762%	$13.5164	$13.52	$13.50	$13.50
Purchase #6	$80.87	10.512%	$89.3711	$89.37	$89.35	$89.40
Purchase #7	$149.87	12.470%	$168.5588	$168.56	$168.55	$168.60
7 purchase totals =	$848.92		$912.5197	$912.52	$912.50	$912.60