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	$103.25	6.130%	$109.5792	$109.58	$109.60	$109.60
Purchase #2	$44.56	7.463%	$47.8855	$47.89	$47.90	$47.90
Purchase #3	$81.80	13.576%	$92.9052	$92.91	$92.90	$92.90
Purchase #4	$228.76	7.361%	$245.599	$245.60	$245.60	$245.60
Purchase #5	$136.55	11.375%	$152.0826	$152.08	$152.10	$152.10
Purchase #6	$194.81	4.470%	$203.518	$203.52	$203.50	$203.50
Purchase #7	$138.88	11.850%	$155.3373	$155.34	$155.35	$155.30
7 purchase totals =	$928.61		$1,006.9068	$1,006.92	$1,006.95	$1,006.90