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	$126.40	12.727%	$142.4869	$142.49	$142.50	$142.50
Purchase #2	$155.69	12.366%	$174.9426	$174.94	$174.95	$174.90
Purchase #3	$208.29	3.855%	$216.3196	$216.32	$216.30	$216.30
Purchase #4	$80.45	13.521%	$91.3276	$91.33	$91.35	$91.30
Purchase #5	$209.69	9.148%	$228.8724	$228.87	$228.85	$228.90
Purchase #6	$52.37	3.442%	$54.1726	$54.17	$54.15	$54.20
Purchase #7	$102.55	10.345%	$113.1588	$113.16	$113.15	$113.20
7 purchase totals =	$935.44		$1,021.2805	$1,021.28	$1,021.25	$1,021.30