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	$164.65	10.124%	$181.3192	$181.32	$181.30	$181.30
Purchase #2	$248.77	5.856%	$263.338	$263.34	$263.35	$263.30
Purchase #3	$146.56	6.453%	$156.0175	$156.02	$156.00	$156.00
Purchase #4	$149.89	6.766%	$160.0316	$160.03	$160.05	$160.00
Purchase #5	$81.31	6.832%	$86.8651	$86.87	$86.85	$86.90
Purchase #6	$128.31	10.760%	$142.1162	$142.12	$142.10	$142.10
Purchase #7	$63.89	5.474%	$67.3873	$67.39	$67.40	$67.40
7 purchase totals =	$983.38		$1,057.0749	$1,057.09	$1,057.05	$1,057.00