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	$160.63	4.189%	$167.3588	$167.36	$167.35	$167.40
Purchase #2	$115.44	10.482%	$127.5404	$127.54	$127.55	$127.50
Purchase #3	$30.61	7.713%	$32.9709	$32.97	$32.95	$33.00
Purchase #4	$32.69	3.664%	$33.8878	$33.89	$33.90	$33.90
Purchase #5	$28.68	4.416%	$29.9465	$29.95	$29.95	$29.90
Purchase #6	$223.37	5.643%	$235.9748	$235.97	$235.95	$236.00
Purchase #7	$89.89	10.223%	$99.0795	$99.08	$99.10	$99.10
7 purchase totals =	$681.31		$726.7587	$726.76	$726.75	$726.80