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	$145.85	7.184%	$156.3279	$156.33	$156.35	$156.30
Purchase #2	$172.76	5.425%	$182.1322	$182.13	$182.15	$182.10
Purchase #3	$78.73	13.449%	$89.3184	$89.32	$89.30	$89.30
Purchase #4	$80.89	3.434%	$83.6678	$83.67	$83.65	$83.70
Purchase #5	$46.63	7.787%	$50.2611	$50.26	$50.25	$50.30
Purchase #6	$160.48	6.606%	$171.0813	$171.08	$171.10	$171.10
Purchase #7	$19.65	8.636%	$21.347	$21.35	$21.35	$21.30
7 purchase totals =	$704.99		$754.1357	$754.14	$754.15	$754.10