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	$237.83	7.741%	$256.2404	$256.24	$256.25	$256.20
Purchase #2	$103.85	3.363%	$107.3425	$107.34	$107.35	$107.30
Purchase #3	$221.82	12.474%	$249.4898	$249.49	$249.50	$249.50
Purchase #4	$206.36	9.652%	$226.2779	$226.28	$226.30	$226.30
Purchase #5	$149.46	12.678%	$168.4085	$168.41	$168.40	$168.40
Purchase #6	$62.56	4.501%	$65.3758	$65.38	$65.40	$65.40
Purchase #7	$86.32	3.844%	$89.6381	$89.64	$89.65	$89.60
7 purchase totals =	$1,068.20		$1,162.7730	$1,162.78	$1,162.85	$1,162.70