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	$168.78	3.621%	$174.8915	$174.89	$174.90	$174.90
Purchase #2	$202.58	12.254%	$227.4042	$227.40	$227.40	$227.40
Purchase #3	$86.41	4.413%	$90.2233	$90.22	$90.20	$90.20
Purchase #4	$45.65	10.787%	$50.5743	$50.57	$50.55	$50.60
Purchase #5	$98.84	10.605%	$109.322	$109.32	$109.30	$109.30
Purchase #6	$195.85	3.723%	$203.1415	$203.14	$203.15	$203.10
Purchase #7	$151.82	3.138%	$156.5841	$156.58	$156.60	$156.60
7 purchase totals =	$949.93		$1,012.1409	$1,012.12	$1,012.10	$1,012.10