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	$215.26	3.390%	$222.5573	$222.56	$222.55	$222.60
Purchase #2	$141.76	9.170%	$154.7594	$154.76	$154.75	$154.80
Purchase #3	$68.36	4.381%	$71.3549	$71.35	$71.35	$71.40
Purchase #4	$97.42	3.754%	$101.0771	$101.08	$101.10	$101.10
Purchase #5	$201.37	3.479%	$208.3757	$208.38	$208.40	$208.40
Purchase #6	$105.31	11.428%	$117.3448	$117.34	$117.35	$117.30
Purchase #7	$53.81	11.221%	$59.848	$59.85	$59.85	$59.80
7 purchase totals =	$883.29		$935.3172	$935.32	$935.35	$935.40