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	$112.75	11.791%	$126.0444	$126.04	$126.05	$126.00
Purchase #2	$240.79	9.335%	$263.2677	$263.27	$263.25	$263.30
Purchase #3	$99.78	9.483%	$109.2421	$109.24	$109.25	$109.20
Purchase #4	$179.39	5.291%	$188.8815	$188.88	$188.90	$188.90
Purchase #5	$159.94	4.279%	$166.7838	$166.78	$166.80	$166.80
Purchase #6	$131.98	7.726%	$142.1768	$142.18	$142.20	$142.20
Purchase #7	$227.53	7.426%	$244.4264	$244.43	$244.45	$244.40
7 purchase totals =	$1,152.16		$1,240.8227	$1,240.82	$1,240.90	$1,240.80