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	$96.81	4.523%	$101.1887	$101.19	$101.20	$101.20
Purchase #2	$74.94	7.273%	$80.3904	$80.39	$80.40	$80.40
Purchase #3	$204.96	7.814%	$220.9756	$220.98	$221.00	$221.00
Purchase #4	$198.63	12.230%	$222.9224	$222.92	$222.90	$222.90
Purchase #5	$223.89	6.447%	$238.3242	$238.32	$238.30	$238.30
Purchase #6	$141.36	7.659%	$152.1868	$152.19	$152.20	$152.20
Purchase #7	$126.27	10.431%	$139.4412	$139.44	$139.45	$139.40
7 purchase totals =	$1,066.86		$1,155.4293	$1,155.43	$1,155.45	$1,155.40