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	$148.36	8.451%	$160.8979	$160.90	$160.90	$160.90
Purchase #2	$202.29	8.116%	$218.7079	$218.71	$218.70	$218.70
Purchase #3	$234.51	12.842%	$264.6258	$264.63	$264.65	$264.60
Purchase #4	$91.49	10.850%	$101.4167	$101.42	$101.40	$101.40
Purchase #5	$106.76	7.271%	$114.5225	$114.52	$114.50	$114.50
Purchase #6	$85.90	5.105%	$90.2852	$90.29	$90.30	$90.30
Purchase #7	$53.94	10.279%	$59.4845	$59.48	$59.50	$59.50
7 purchase totals =	$923.25		$1,009.9405	$1,009.95	$1,009.95	$1,009.90