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	$150.89	3.373%	$155.9795	$155.98	$156.00	$156.00
Purchase #2	$188.65	4.130%	$196.4412	$196.44	$196.45	$196.40
Purchase #3	$209.26	12.106%	$234.593	$234.59	$234.60	$234.60
Purchase #4	$90.94	9.331%	$99.4256	$99.43	$99.45	$99.40
Purchase #5	$212.37	3.236%	$219.2423	$219.24	$219.25	$219.20
Purchase #6	$224.28	11.713%	$250.5499	$250.55	$250.55	$250.50
Purchase #7	$78.34	7.844%	$84.485	$84.49	$84.50	$84.50
7 purchase totals =	$1,154.73		$1,240.7165	$1,240.72	$1,240.80	$1,240.60