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	$167.40	10.211%	$184.4932	$184.49	$184.50	$184.50
Purchase #2	$103.98	13.534%	$118.0527	$118.05	$118.05	$118.10
Purchase #3	$171.94	9.621%	$188.4823	$188.48	$188.50	$188.50
Purchase #4	$79.28	7.520%	$85.2419	$85.24	$85.25	$85.20
Purchase #5	$164.84	9.566%	$180.6086	$180.61	$180.60	$180.60
Purchase #6	$169.37	6.112%	$179.7219	$179.72	$179.70	$179.70
Purchase #7	$162.82	6.300%	$173.0777	$173.08	$173.10	$173.10
7 purchase totals =	$1,019.63		$1,109.6783	$1,109.67	$1,109.70	$1,109.70