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	$215.30	5.727%	$227.6302	$227.63	$227.65	$227.60
Purchase #2	$84.69	5.546%	$89.3869	$89.39	$89.40	$89.40
Purchase #3	$228.91	3.737%	$237.4644	$237.46	$237.45	$237.50
Purchase #4	$240.28	9.614%	$263.3805	$263.38	$263.40	$263.40
Purchase #5	$79.47	3.254%	$82.056	$82.06	$82.05	$82.10
Purchase #6	$54.67	13.306%	$61.9444	$61.94	$61.95	$61.90
Purchase #7	$160.60	9.526%	$175.8988	$175.90	$175.90	$175.90
7 purchase totals =	$1,063.92		$1,137.7612	$1,137.76	$1,137.80	$1,137.80