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	$101.73	3.379%	$105.1675	$105.17	$105.15	$105.20
Purchase #2	$146.56	6.723%	$156.4132	$156.41	$156.40	$156.40
Purchase #3	$81.49	6.312%	$86.6336	$86.63	$86.65	$86.60
Purchase #4	$250.56	3.134%	$258.4126	$258.41	$258.40	$258.40
Purchase #5	$207.33	11.667%	$231.5192	$231.52	$231.50	$231.50
Purchase #6	$40.39	12.868%	$45.5874	$45.59	$45.60	$45.60
Purchase #7	$55.31	11.611%	$61.732	$61.73	$61.75	$61.70
7 purchase totals =	$883.37		$945.4655	$945.46	$945.45	$945.40