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	$76.38	3.369%	$78.9532	$78.95	$78.95	$79.00
Purchase #2	$96.37	13.648%	$109.5226	$109.52	$109.50	$109.50
Purchase #3	$49.40	7.681%	$53.1944	$53.19	$53.20	$53.20
Purchase #4	$37.44	11.621%	$41.7909	$41.79	$41.80	$41.80
Purchase #5	$136.25	11.107%	$151.3833	$151.38	$151.40	$151.40
Purchase #6	$38.81	11.555%	$43.2945	$43.29	$43.30	$43.30
Purchase #7	$222.76	6.356%	$236.9186	$236.92	$236.90	$236.90
7 purchase totals =	$657.41		$715.0575	$715.04	$715.05	$715.10