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	$210.54	4.513%	$220.0417	$220.04	$220.05	$220.00
Purchase #2	$68.61	5.623%	$72.4679	$72.47	$72.45	$72.50
Purchase #3	$53.69	9.452%	$58.7648	$58.76	$58.75	$58.80
Purchase #4	$197.96	10.682%	$219.1061	$219.11	$219.10	$219.10
Purchase #5	$105.82	4.379%	$110.4539	$110.45	$110.45	$110.50
Purchase #6	$171.93	6.384%	$182.906	$182.91	$182.90	$182.90
Purchase #7	$101.90	12.429%	$114.5652	$114.57	$114.55	$114.60
7 purchase totals =	$910.45		$978.3056	$978.31	$978.25	$978.40