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	$182.37	4.155%	$189.9475	$189.95	$189.95	$189.90
Purchase #2	$158.67	8.274%	$171.7984	$171.80	$171.80	$171.80
Purchase #3	$129.46	7.668%	$139.387	$139.39	$139.40	$139.40
Purchase #4	$189.65	6.693%	$202.3433	$202.34	$202.35	$202.30
Purchase #5	$126.54	7.782%	$136.3873	$136.39	$136.40	$136.40
Purchase #6	$64.49	12.171%	$72.3391	$72.34	$72.35	$72.30
Purchase #7	$144.54	12.166%	$162.1247	$162.12	$162.10	$162.10
7 purchase totals =	$995.72		$1,074.3273	$1,074.33	$1,074.35	$1,074.20