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	$178.53	7.176%	$191.3413	$191.34	$191.35	$191.30
Purchase #2	$196.65	6.767%	$209.9573	$209.96	$209.95	$210.00
Purchase #3	$164.57	9.292%	$179.8618	$179.86	$179.85	$179.90
Purchase #4	$99.27	6.402%	$105.6253	$105.63	$105.65	$105.60
Purchase #5	$189.66	4.565%	$198.318	$198.32	$198.30	$198.30
Purchase #6	$220.72	9.241%	$241.1167	$241.12	$241.10	$241.10
Purchase #7	$26.86	10.158%	$29.5884	$29.59	$29.60	$29.60
7 purchase totals =	$1,076.26		$1,155.8088	$1,155.82	$1,155.80	$1,155.80