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	$145.66	11.791%	$162.8348	$162.83	$162.85	$162.80
Purchase #2	$74.64	3.709%	$77.4084	$77.41	$77.40	$77.40
Purchase #3	$106.76	5.647%	$112.7887	$112.79	$112.80	$112.80
Purchase #4	$145.98	7.577%	$157.0409	$157.04	$157.05	$157.00
Purchase #5	$194.90	13.250%	$220.7243	$220.72	$220.70	$220.70
Purchase #6	$136.62	12.343%	$153.483	$153.48	$153.50	$153.50
Purchase #7	$181.95	8.113%	$196.7116	$196.71	$196.70	$196.70
7 purchase totals =	$986.51		$1,080.9917	$1,080.98	$1,081.00	$1,080.90