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	$191.27	4.597%	$200.0627	$200.06	$200.05	$200.10
Purchase #2	$92.96	5.442%	$98.0189	$98.02	$98.00	$98.00
Purchase #3	$95.31	10.669%	$105.4786	$105.48	$105.50	$105.50
Purchase #4	$44.40	13.460%	$50.3762	$50.38	$50.40	$50.40
Purchase #5	$26.68	4.601%	$27.9075	$27.91	$27.90	$27.90
Purchase #6	$62.56	6.231%	$66.4581	$66.46	$66.45	$66.50
Purchase #7	$68.95	4.258%	$71.8859	$71.89	$71.90	$71.90
7 purchase totals =	$582.13		$620.1879	$620.20	$620.20	$620.30