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	$56.41	6.210%	$59.9131	$59.91	$59.90	$59.90
Purchase #2	$186.45	3.126%	$192.2784	$192.28	$192.30	$192.30
Purchase #3	$68.97	6.524%	$73.4696	$73.47	$73.45	$73.50
Purchase #4	$145.57	4.496%	$152.1148	$152.11	$152.10	$152.10
Purchase #5	$221.80	5.483%	$233.9613	$233.96	$233.95	$234.00
Purchase #6	$149.30	7.505%	$160.505	$160.51	$160.50	$160.50
Purchase #7	$230.66	3.786%	$239.3928	$239.39	$239.40	$239.40
7 purchase totals =	$1,059.16		$1,111.6350	$1,111.63	$1,111.60	$1,111.70