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	$148.69	5.829%	$157.3571	$157.36	$157.35	$157.40
Purchase #2	$70.41	9.771%	$77.2898	$77.29	$77.30	$77.30
Purchase #3	$193.69	5.629%	$204.5928	$204.59	$204.60	$204.60
Purchase #4	$164.55	13.836%	$187.3171	$187.32	$187.30	$187.30
Purchase #5	$227.92	7.713%	$245.4995	$245.50	$245.50	$245.50
Purchase #6	$82.94	4.577%	$86.7362	$86.74	$86.75	$86.70
Purchase #7	$18.81	6.855%	$20.0994	$20.10	$20.10	$20.10
7 purchase totals =	$907.01		$978.8919	$978.90	$978.90	$978.90