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	$99.65	6.293%	$105.921	$105.92	$105.90	$105.90
Purchase #2	$27.67	11.748%	$30.9207	$30.92	$30.90	$30.90
Purchase #3	$93.92	12.156%	$105.3369	$105.34	$105.35	$105.30
Purchase #4	$100.93	9.582%	$110.6011	$110.60	$110.60	$110.60
Purchase #5	$75.98	3.745%	$78.8255	$78.83	$78.85	$78.80
Purchase #6	$52.34	11.430%	$58.3225	$58.32	$58.30	$58.30
Purchase #7	$31.29	4.281%	$32.6295	$32.63	$32.65	$32.60
7 purchase totals =	$481.78		$522.5572	$522.56	$522.55	$522.40