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	$146.89	3.660%	$152.2662	$152.27	$152.25	$152.30
Purchase #2	$114.37	10.355%	$126.213	$126.21	$126.20	$126.20
Purchase #3	$79.58	4.155%	$82.8865	$82.89	$82.90	$82.90
Purchase #4	$189.44	11.122%	$210.5095	$210.51	$210.50	$210.50
Purchase #5	$52.75	7.670%	$56.7959	$56.80	$56.80	$56.80
Purchase #6	$67.95	12.201%	$76.2406	$76.24	$76.25	$76.20
Purchase #7	$128.97	10.434%	$142.4267	$142.43	$142.45	$142.40
7 purchase totals =	$779.95		$847.3384	$847.35	$847.35	$847.30