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	$156.27	11.680%	$174.5223	$174.52	$174.50	$174.50
Purchase #2	$10.48	8.658%	$11.3874	$11.39	$11.40	$11.40
Purchase #3	$20.35	9.589%	$22.3014	$22.30	$22.30	$22.30
Purchase #4	$73.98	6.602%	$78.8642	$78.86	$78.85	$78.90
Purchase #5	$24.69	11.315%	$27.4837	$27.48	$27.50	$27.50
Purchase #6	$18.46	5.120%	$19.4052	$19.41	$19.40	$19.40
Purchase #7	$64.88	10.299%	$71.562	$71.56	$71.55	$71.60
7 purchase totals =	$369.11		$405.5262	$405.52	$405.50	$405.60