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	$166.45	8.218%	$180.1289	$180.13	$180.15	$180.10
Purchase #2	$166.81	4.864%	$174.9236	$174.92	$174.90	$174.90
Purchase #3	$183.41	4.768%	$192.155	$192.16	$192.15	$192.20
Purchase #4	$168.57	13.772%	$191.7855	$191.79	$191.80	$191.80
Purchase #5	$86.30	8.861%	$93.947	$93.95	$93.95	$93.90
Purchase #6	$75.37	13.786%	$85.7605	$85.76	$85.75	$85.80
Purchase #7	$172.27	10.470%	$190.3067	$190.31	$190.30	$190.30
7 purchase totals =	$1,019.18		$1,109.0072	$1,109.02	$1,109.00	$1,109.00