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	$204.38	7.341%	$219.3835	$219.38	$219.40	$219.40
Purchase #2	$80.96	3.656%	$83.9199	$83.92	$83.90	$83.90
Purchase #3	$223.35	12.127%	$250.4357	$250.44	$250.45	$250.40
Purchase #4	$145.59	12.346%	$163.5645	$163.56	$163.55	$163.60
Purchase #5	$71.31	13.164%	$80.6972	$80.70	$80.70	$80.70
Purchase #6	$76.53	3.109%	$78.9093	$78.91	$78.90	$78.90
Purchase #7	$165.76	12.600%	$186.6458	$186.65	$186.65	$186.60
7 purchase totals =	$967.88		$1,063.5559	$1,063.56	$1,063.55	$1,063.50