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	$240.31	11.222%	$267.2776	$267.28	$267.30	$267.30
Purchase #2	$70.67	13.776%	$80.4055	$80.41	$80.40	$80.40
Purchase #3	$150.56	3.672%	$156.0886	$156.09	$156.10	$156.10
Purchase #4	$216.29	3.221%	$223.2567	$223.26	$223.25	$223.30
Purchase #5	$51.26	6.593%	$54.6396	$54.64	$54.65	$54.60
Purchase #6	$202.44	6.854%	$216.3152	$216.32	$216.30	$216.30
Purchase #7	$29.60	6.367%	$31.4846	$31.48	$31.50	$31.50
7 purchase totals =	$961.13		$1,029.4678	$1,029.48	$1,029.50	$1,029.50