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	$145.56	11.511%	$162.3154	$162.32	$162.30	$162.30
Purchase #2	$86.96	10.399%	$96.003	$96.00	$96.00	$96.00
Purchase #3	$8.93	3.139%	$9.2103	$9.21	$9.20	$9.20
Purchase #4	$57.70	5.736%	$61.0097	$61.01	$61.00	$61.00
Purchase #5	$208.44	4.139%	$217.0673	$217.07	$217.05	$217.10
Purchase #6	$192.88	12.442%	$216.8781	$216.88	$216.90	$216.90
Purchase #7	$192.93	11.797%	$215.69	$215.69	$215.70	$215.70
7 purchase totals =	$893.40		$978.1738	$978.18	$978.15	$978.20