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	$162.76	13.761%	$185.1574	$185.16	$185.15	$185.20
Purchase #2	$35.32	7.773%	$38.0654	$38.07	$38.05	$38.10
Purchase #3	$249.90	10.841%	$276.9917	$276.99	$277.00	$277.00
Purchase #4	$60.90	5.309%	$64.1332	$64.13	$64.15	$64.10
Purchase #5	$101.70	11.432%	$113.3263	$113.33	$113.35	$113.30
Purchase #6	$144.69	8.334%	$156.7485	$156.75	$156.75	$156.70
Purchase #7	$175.45	3.538%	$181.6574	$181.66	$181.65	$181.70
7 purchase totals =	$930.72		$1,016.0799	$1,016.09	$1,016.10	$1,016.10