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	$105.74	3.351%	$109.2833	$109.28	$109.30	$109.30
Purchase #2	$229.65	6.775%	$245.2088	$245.21	$245.20	$245.20
Purchase #3	$107.56	6.853%	$114.9311	$114.93	$114.95	$114.90
Purchase #4	$69.58	4.258%	$72.5427	$72.54	$72.55	$72.50
Purchase #5	$31.30	3.351%	$32.3489	$32.35	$32.35	$32.30
Purchase #6	$134.67	5.538%	$142.128	$142.13	$142.15	$142.10
Purchase #7	$47.60	12.147%	$53.382	$53.38	$53.40	$53.40
7 purchase totals =	$726.10		$769.8248	$769.82	$769.90	$769.70