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	$51.38	4.205%	$53.5405	$53.54	$53.55	$53.50
Purchase #2	$187.87	4.384%	$196.1062	$196.11	$196.10	$196.10
Purchase #3	$51.52	11.526%	$57.4582	$57.46	$57.45	$57.50
Purchase #4	$101.32	13.690%	$115.1907	$115.19	$115.20	$115.20
Purchase #5	$249.96	7.533%	$268.7895	$268.79	$268.80	$268.80
Purchase #6	$241.70	11.827%	$270.2859	$270.29	$270.30	$270.30
Purchase #7	$50.45	12.319%	$56.6649	$56.66	$56.65	$56.70
7 purchase totals =	$934.20		$1,018.0359	$1,018.04	$1,018.05	$1,018.10