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	$35.72	10.549%	$39.4881	$39.49	$39.50	$39.50
Purchase #2	$196.47	9.500%	$215.1347	$215.13	$215.15	$215.10
Purchase #3	$100.31	3.818%	$104.1398	$104.14	$104.15	$104.10
Purchase #4	$70.90	4.349%	$73.9834	$73.98	$74.00	$74.00
Purchase #5	$178.38	8.572%	$193.6707	$193.67	$193.65	$193.70
Purchase #6	$171.56	8.103%	$185.4615	$185.46	$185.45	$185.50
Purchase #7	$227.92	10.107%	$250.9559	$250.96	$250.95	$251.00
7 purchase totals =	$981.26		$1,062.8341	$1,062.83	$1,062.85	$1,062.90