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	$206.66	5.462%	$217.9478	$217.95	$217.95	$217.90
Purchase #2	$49.76	11.828%	$55.6456	$55.65	$55.65	$55.60
Purchase #3	$98.73	10.670%	$109.2645	$109.26	$109.25	$109.30
Purchase #4	$184.53	9.372%	$201.8242	$201.82	$201.80	$201.80
Purchase #5	$67.46	6.594%	$71.9083	$71.91	$71.90	$71.90
Purchase #6	$200.59	4.578%	$209.773	$209.77	$209.75	$209.80
Purchase #7	$211.53	10.608%	$233.9691	$233.97	$233.95	$234.00
7 purchase totals =	$1,019.26		$1,100.3325	$1,100.33	$1,100.25	$1,100.30