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	$241.59	3.197%	$249.3136	$249.31	$249.30	$249.30
Purchase #2	$244.97	9.563%	$268.3965	$268.40	$268.40	$268.40
Purchase #3	$220.41	3.594%	$228.3315	$228.33	$228.35	$228.30
Purchase #4	$39.62	3.350%	$40.9473	$40.95	$40.95	$40.90
Purchase #5	$43.65	4.208%	$45.4868	$45.49	$45.50	$45.50
Purchase #6	$204.59	3.504%	$211.7588	$211.76	$211.75	$211.80
Purchase #7	$86.60	3.670%	$89.7782	$89.78	$89.80	$89.80
7 purchase totals =	$1,081.43		$1,134.0127	$1,134.02	$1,134.05	$1,134.00