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	$208.96	6.433%	$222.4024	$222.40	$222.40	$222.40
Purchase #2	$91.95	6.789%	$98.1925	$98.19	$98.20	$98.20
Purchase #3	$101.28	8.345%	$109.7318	$109.73	$109.75	$109.70
Purchase #4	$222.70	8.148%	$240.8456	$240.85	$240.85	$240.80
Purchase #5	$203.42	8.759%	$221.2376	$221.24	$221.25	$221.20
Purchase #6	$94.56	12.558%	$106.4348	$106.43	$106.45	$106.40
Purchase #7	$142.76	6.231%	$151.6554	$151.66	$151.65	$151.70
7 purchase totals =	$1,065.63		$1,150.5001	$1,150.50	$1,150.55	$1,150.40