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	$181.69	8.232%	$196.6467	$196.65	$196.65	$196.60
Purchase #2	$86.34	8.490%	$93.6703	$93.67	$93.65	$93.70
Purchase #3	$79.27	5.734%	$83.8153	$83.82	$83.80	$83.80
Purchase #4	$72.78	12.680%	$82.0085	$82.01	$82.00	$82.00
Purchase #5	$86.31	12.278%	$96.9071	$96.91	$96.90	$96.90
Purchase #6	$216.31	12.375%	$243.0784	$243.08	$243.10	$243.10
Purchase #7	$171.26	8.768%	$186.2761	$186.28	$186.30	$186.30
7 purchase totals =	$893.96		$982.4024	$982.42	$982.40	$982.40