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	$61.53	5.414%	$64.8612	$64.86	$64.85	$64.90
Purchase #2	$140.85	10.192%	$155.2054	$155.21	$155.20	$155.20
Purchase #3	$131.32	10.228%	$144.7514	$144.75	$144.75	$144.80
Purchase #4	$163.45	12.152%	$183.3124	$183.31	$183.30	$183.30
Purchase #5	$83.51	9.716%	$91.6238	$91.62	$91.60	$91.60
Purchase #6	$205.91	10.374%	$227.2711	$227.27	$227.25	$227.30
Purchase #7	$237.69	9.792%	$260.9646	$260.96	$260.95	$261.00
7 purchase totals =	$1,024.26		$1,127.9899	$1,127.98	$1,127.90	$1,128.10