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	$141.34	4.436%	$147.6098	$147.61	$147.60	$147.60
Purchase #2	$39.49	7.403%	$42.4134	$42.41	$42.40	$42.40
Purchase #3	$36.59	6.146%	$38.8388	$38.84	$38.85	$38.80
Purchase #4	$44.89	10.844%	$49.7579	$49.76	$49.75	$49.80
Purchase #5	$123.52	3.483%	$127.8222	$127.82	$127.80	$127.80
Purchase #6	$56.33	7.291%	$60.437	$60.44	$60.45	$60.40
Purchase #7	$229.81	12.815%	$259.2602	$259.26	$259.25	$259.30
7 purchase totals =	$671.97		$726.1393	$726.14	$726.10	$726.10