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	$210.65	9.123%	$229.8676	$229.87	$229.85	$229.90
Purchase #2	$148.64	6.637%	$158.5052	$158.51	$158.50	$158.50
Purchase #3	$177.26	4.543%	$185.3129	$185.31	$185.30	$185.30
Purchase #4	$142.51	9.723%	$156.3662	$156.37	$156.35	$156.40
Purchase #5	$168.56	8.221%	$182.4173	$182.42	$182.40	$182.40
Purchase #6	$84.90	8.364%	$92.001	$92.00	$92.00	$92.00
Purchase #7	$205.88	6.536%	$219.3363	$219.34	$219.35	$219.30
7 purchase totals =	$1,138.40		$1,223.8065	$1,223.82	$1,223.75	$1,223.80