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	$122.37	9.155%	$133.573	$133.57	$133.55	$133.60
Purchase #2	$147.43	8.475%	$159.9247	$159.92	$159.90	$159.90
Purchase #3	$195.28	4.493%	$204.0539	$204.05	$204.05	$204.10
Purchase #4	$172.59	13.747%	$196.3159	$196.32	$196.30	$196.30
Purchase #5	$91.97	8.440%	$99.7323	$99.73	$99.75	$99.70
Purchase #6	$88.43	10.382%	$97.6108	$97.61	$97.60	$97.60
Purchase #7	$156.87	9.421%	$171.6487	$171.65	$171.65	$171.60
7 purchase totals =	$974.94		$1,062.8593	$1,062.85	$1,062.80	$1,062.80