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	$72.60	13.812%	$82.6275	$82.63	$82.65	$82.60
Purchase #2	$212.71	3.705%	$220.5909	$220.59	$220.60	$220.60
Purchase #3	$180.27	4.774%	$188.8761	$188.88	$188.90	$188.90
Purchase #4	$197.76	6.552%	$210.7172	$210.72	$210.70	$210.70
Purchase #5	$194.66	9.827%	$213.7892	$213.79	$213.80	$213.80
Purchase #6	$208.39	3.566%	$215.8212	$215.82	$215.80	$215.80
Purchase #7	$80.91	13.871%	$92.133	$92.13	$92.15	$92.10
7 purchase totals =	$1,147.30		$1,224.5551	$1,224.56	$1,224.60	$1,224.50