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	$210.37	4.741%	$220.3436	$220.34	$220.35	$220.30
Purchase #2	$82.48	8.242%	$89.278	$89.28	$89.30	$89.30
Purchase #3	$126.76	6.222%	$134.647	$134.65	$134.65	$134.60
Purchase #4	$163.72	13.521%	$185.8566	$185.86	$185.85	$185.90
Purchase #5	$78.95	7.696%	$85.026	$85.03	$85.05	$85.00
Purchase #6	$72.67	10.424%	$80.2451	$80.25	$80.25	$80.20
Purchase #7	$39.47	6.477%	$42.0265	$42.03	$42.05	$42.00
7 purchase totals =	$774.42		$837.4228	$837.44	$837.50	$837.30