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	$82.60	10.547%	$91.3118	$91.31	$91.30	$91.30
Purchase #2	$156.85	7.309%	$168.3142	$168.31	$168.30	$168.30
Purchase #3	$14.86	6.578%	$15.8375	$15.84	$15.85	$15.80
Purchase #4	$233.79	7.132%	$250.4639	$250.46	$250.45	$250.50
Purchase #5	$231.29	8.285%	$250.4524	$250.45	$250.45	$250.50
Purchase #6	$179.59	7.299%	$192.6983	$192.70	$192.70	$192.70
Purchase #7	$213.78	7.318%	$229.4244	$229.42	$229.40	$229.40
7 purchase totals =	$1,112.76		$1,198.5025	$1,198.49	$1,198.45	$1,198.50