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	$175.25	6.313%	$186.3135	$186.31	$186.30	$186.30
Purchase #2	$187.66	7.790%	$202.2787	$202.28	$202.30	$202.30
Purchase #3	$84.28	6.255%	$89.5517	$89.55	$89.55	$89.60
Purchase #4	$51.99	5.625%	$54.9144	$54.91	$54.90	$54.90
Purchase #5	$184.28	6.805%	$196.8203	$196.82	$196.80	$196.80
Purchase #6	$162.35	5.714%	$171.6267	$171.63	$171.65	$171.60
Purchase #7	$95.97	10.529%	$106.0747	$106.07	$106.05	$106.10
7 purchase totals =	$941.78		$1,007.5800	$1,007.57	$1,007.55	$1,007.60