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	$158.62	9.824%	$174.2028	$174.20	$174.20	$174.20
Purchase #2	$168.42	7.561%	$181.1542	$181.15	$181.15	$181.20
Purchase #3	$53.50	11.755%	$59.7889	$59.79	$59.80	$59.80
Purchase #4	$53.80	10.468%	$59.4318	$59.43	$59.45	$59.40
Purchase #5	$220.58	13.229%	$249.7605	$249.76	$249.75	$249.80
Purchase #6	$150.44	5.494%	$158.7052	$158.71	$158.70	$158.70
Purchase #7	$101.56	3.409%	$105.0222	$105.02	$105.00	$105.00
7 purchase totals =	$906.92		$988.0656	$988.06	$988.05	$988.10