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	$105.31	6.246%	$111.8877	$111.89	$111.90	$111.90
Purchase #2	$212.61	7.400%	$228.3431	$228.34	$228.35	$228.30
Purchase #3	$168.45	11.103%	$187.153	$187.15	$187.15	$187.20
Purchase #4	$193.32	11.859%	$216.2458	$216.25	$216.25	$216.20
Purchase #5	$84.73	13.631%	$96.2795	$96.28	$96.30	$96.30
Purchase #6	$111.79	4.801%	$117.157	$117.16	$117.15	$117.20
Purchase #7	$113.56	5.147%	$119.4049	$119.40	$119.40	$119.40
7 purchase totals =	$989.77		$1,076.4710	$1,076.47	$1,076.50	$1,076.50