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	$66.79	8.611%	$72.5413	$72.54	$72.55	$72.50
Purchase #2	$28.90	13.759%	$32.8764	$32.88	$32.90	$32.90
Purchase #3	$243.96	8.302%	$264.2136	$264.21	$264.20	$264.20
Purchase #4	$229.83	10.445%	$253.8357	$253.84	$253.85	$253.80
Purchase #5	$118.92	3.461%	$123.0358	$123.04	$123.05	$123.00
Purchase #6	$154.65	3.465%	$160.0086	$160.01	$160.00	$160.00
Purchase #7	$54.66	8.867%	$59.5067	$59.51	$59.50	$59.50
7 purchase totals =	$897.71		$966.0181	$966.03	$966.05	$965.90