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	$109.93	6.573%	$117.1557	$117.16	$117.15	$117.20
Purchase #2	$86.93	10.608%	$96.1515	$96.15	$96.15	$96.20
Purchase #3	$43.86	6.157%	$46.5605	$46.56	$46.55	$46.60
Purchase #4	$68.76	13.742%	$78.209	$78.21	$78.20	$78.20
Purchase #5	$168.54	9.326%	$184.258	$184.26	$184.25	$184.30
Purchase #6	$240.92	6.578%	$256.7677	$256.77	$256.75	$256.80
Purchase #7	$78.27	5.134%	$82.2884	$82.29	$82.30	$82.30
7 purchase totals =	$797.21		$861.3908	$861.40	$861.35	$861.60