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	$204.26	9.266%	$223.1867	$223.19	$223.20	$223.20
Purchase #2	$104.89	13.557%	$119.1099	$119.11	$119.10	$119.10
Purchase #3	$42.28	13.146%	$47.8381	$47.84	$47.85	$47.80
Purchase #4	$183.54	6.864%	$196.1382	$196.14	$196.15	$196.10
Purchase #5	$170.63	13.466%	$193.607	$193.61	$193.60	$193.60
Purchase #6	$132.31	3.466%	$136.8959	$136.90	$136.90	$136.90
Purchase #7	$168.50	10.597%	$186.3559	$186.36	$186.35	$186.40
7 purchase totals =	$1,006.41		$1,103.1317	$1,103.15	$1,103.15	$1,103.10