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	$159.41	6.133%	$169.1866	$169.19	$169.20	$169.20
Purchase #2	$54.67	8.647%	$59.3973	$59.40	$59.40	$59.40
Purchase #3	$128.36	3.177%	$132.438	$132.44	$132.45	$132.40
Purchase #4	$174.95	12.539%	$196.887	$196.89	$196.90	$196.90
Purchase #5	$98.39	9.700%	$107.9338	$107.93	$107.95	$107.90
Purchase #6	$247.30	9.638%	$271.1348	$271.13	$271.15	$271.10
Purchase #7	$101.71	11.651%	$113.5602	$113.56	$113.55	$113.60
7 purchase totals =	$964.79		$1,050.5377	$1,050.54	$1,050.60	$1,050.50