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	$187.97	4.822%	$197.0339	$197.03	$197.05	$197.00
Purchase #2	$174.58	6.269%	$185.5244	$185.52	$185.50	$185.50
Purchase #3	$228.53	11.446%	$254.6875	$254.69	$254.70	$254.70
Purchase #4	$21.69	12.742%	$24.4537	$24.45	$24.45	$24.50
Purchase #5	$69.87	11.801%	$78.1154	$78.12	$78.10	$78.10
Purchase #6	$36.71	5.835%	$38.852	$38.85	$38.85	$38.90
Purchase #7	$52.32	10.181%	$57.6467	$57.65	$57.65	$57.60
7 purchase totals =	$771.67		$836.3136	$836.31	$836.30	$836.30