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	$235.30	3.486%	$243.5026	$243.50	$243.50	$243.50
Purchase #2	$47.32	3.586%	$49.0169	$49.02	$49.00	$49.00
Purchase #3	$63.63	13.740%	$72.3728	$72.37	$72.35	$72.40
Purchase #4	$163.70	7.373%	$175.7696	$175.77	$175.75	$175.80
Purchase #5	$181.99	8.217%	$196.9441	$196.94	$196.95	$196.90
Purchase #6	$149.43	9.826%	$164.113	$164.11	$164.10	$164.10
Purchase #7	$171.80	10.524%	$189.8802	$189.88	$189.90	$189.90
7 purchase totals =	$1,013.17		$1,091.5992	$1,091.59	$1,091.55	$1,091.60