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	$189.71	11.872%	$212.2324	$212.23	$212.25	$212.20
Purchase #2	$190.38	12.357%	$213.9053	$213.91	$213.90	$213.90
Purchase #3	$103.64	7.720%	$111.641	$111.64	$111.65	$111.60
Purchase #4	$124.32	13.303%	$140.8583	$140.86	$140.85	$140.90
Purchase #5	$62.61	10.591%	$69.241	$69.24	$69.25	$69.20
Purchase #6	$129.44	9.572%	$141.83	$141.83	$141.85	$141.80
Purchase #7	$202.97	5.217%	$213.5589	$213.56	$213.55	$213.60
7 purchase totals =	$1,003.07		$1,103.2669	$1,103.27	$1,103.30	$1,103.20