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	$149.71	9.353%	$163.7124	$163.71	$163.70	$163.70
Purchase #2	$54.94	4.349%	$57.3293	$57.33	$57.35	$57.30
Purchase #3	$53.51	10.406%	$59.0783	$59.08	$59.10	$59.10
Purchase #4	$212.54	5.668%	$224.5868	$224.59	$224.60	$224.60
Purchase #5	$82.85	7.755%	$89.275	$89.28	$89.30	$89.30
Purchase #6	$206.96	6.152%	$219.6922	$219.69	$219.70	$219.70
Purchase #7	$245.64	12.325%	$275.9151	$275.92	$275.90	$275.90
7 purchase totals =	$1,006.15		$1,089.5891	$1,089.60	$1,089.65	$1,089.60