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	$55.85	9.769%	$61.306	$61.31	$61.30	$61.30
Purchase #2	$170.86	13.304%	$193.5912	$193.59	$193.60	$193.60
Purchase #3	$88.68	13.774%	$100.8948	$100.89	$100.90	$100.90
Purchase #4	$47.42	12.463%	$53.33	$53.33	$53.35	$53.30
Purchase #5	$238.94	7.524%	$256.9178	$256.92	$256.90	$256.90
Purchase #6	$156.77	3.692%	$162.5579	$162.56	$162.55	$162.60
Purchase #7	$135.42	9.297%	$148.01	$148.01	$148.00	$148.00
7 purchase totals =	$893.94		$976.6077	$976.61	$976.60	$976.60