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	$93.85	4.360%	$97.9419	$97.94	$97.95	$97.90
Purchase #2	$83.56	7.771%	$90.0534	$90.05	$90.05	$90.10
Purchase #3	$89.46	7.608%	$96.2661	$96.27	$96.25	$96.30
Purchase #4	$138.78	13.112%	$156.9768	$156.98	$157.00	$157.00
Purchase #5	$210.48	3.362%	$217.5563	$217.56	$217.55	$217.60
Purchase #6	$194.98	6.314%	$207.291	$207.29	$207.30	$207.30
Purchase #7	$74.34	5.380%	$78.3395	$78.34	$78.35	$78.30
7 purchase totals =	$885.45		$944.4250	$944.43	$944.45	$944.50