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	$143.53	6.451%	$152.7891	$152.79	$152.80	$152.80
Purchase #2	$75.75	12.776%	$85.4278	$85.43	$85.45	$85.40
Purchase #3	$118.89	13.780%	$135.273	$135.27	$135.25	$135.30
Purchase #4	$82.43	12.441%	$92.6851	$92.69	$92.70	$92.70
Purchase #5	$216.54	7.858%	$233.5557	$233.56	$233.55	$233.60
Purchase #6	$238.34	5.236%	$250.8195	$250.82	$250.80	$250.80
Purchase #7	$112.56	9.445%	$123.1913	$123.19	$123.20	$123.20
7 purchase totals =	$988.04		$1,073.7415	$1,073.75	$1,073.75	$1,073.80