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	$227.99	4.740%	$238.7967	$238.80	$238.80	$238.80
Purchase #2	$226.37	5.862%	$239.6398	$239.64	$239.65	$239.60
Purchase #3	$67.33	5.705%	$71.1712	$71.17	$71.15	$71.20
Purchase #4	$21.66	13.749%	$24.638	$24.64	$24.65	$24.60
Purchase #5	$149.52	12.740%	$168.5688	$168.57	$168.55	$168.60
Purchase #6	$86.46	5.793%	$91.4686	$91.47	$91.45	$91.50
Purchase #7	$150.76	13.771%	$171.5212	$171.52	$171.50	$171.50
7 purchase totals =	$930.09		$1,005.8043	$1,005.81	$1,005.75	$1,005.80