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	$200.62	4.805%	$210.2598	$210.26	$210.25	$210.30
Purchase #2	$64.82	4.204%	$67.545	$67.55	$67.55	$67.50
Purchase #3	$80.26	12.443%	$90.2468	$90.25	$90.25	$90.20
Purchase #4	$244.25	4.326%	$254.8163	$254.82	$254.80	$254.80
Purchase #5	$42.76	9.676%	$46.8975	$46.90	$46.90	$46.90
Purchase #6	$100.44	12.321%	$112.8152	$112.82	$112.80	$112.80
Purchase #7	$165.96	9.752%	$182.1444	$182.14	$182.15	$182.10
7 purchase totals =	$899.11		$964.7250	$964.74	$964.70	$964.60