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	$135.41	13.627%	$153.8623	$153.86	$153.85	$153.90
Purchase #2	$231.29	3.265%	$238.8416	$238.84	$238.85	$238.80
Purchase #3	$163.61	3.367%	$169.1187	$169.12	$169.10	$169.10
Purchase #4	$167.41	5.197%	$176.1103	$176.11	$176.10	$176.10
Purchase #5	$97.89	7.579%	$105.3091	$105.31	$105.30	$105.30
Purchase #6	$38.68	7.272%	$41.4928	$41.49	$41.50	$41.50
Purchase #7	$249.28	6.498%	$265.4782	$265.48	$265.50	$265.50
7 purchase totals =	$1,083.57		$1,150.2130	$1,150.21	$1,150.20	$1,150.20