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	$189.35	3.687%	$196.3313	$196.33	$196.35	$196.30
Purchase #2	$140.44	13.205%	$158.9851	$158.99	$159.00	$159.00
Purchase #3	$28.46	12.442%	$32.001	$32.00	$32.00	$32.00
Purchase #4	$184.49	8.805%	$200.7343	$200.73	$200.75	$200.70
Purchase #5	$174.27	7.648%	$187.5982	$187.60	$187.60	$187.60
Purchase #6	$53.48	12.582%	$60.2089	$60.21	$60.20	$60.20
Purchase #7	$153.36	9.654%	$168.1654	$168.17	$168.15	$168.20
7 purchase totals =	$923.85		$1,004.0242	$1,004.03	$1,004.05	$1,004.00