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	$232.90	13.747%	$264.9168	$264.92	$264.90	$264.90
Purchase #2	$168.82	10.547%	$186.6254	$186.63	$186.65	$186.60
Purchase #3	$71.70	12.782%	$80.8647	$80.86	$80.85	$80.90
Purchase #4	$53.27	5.516%	$56.2084	$56.21	$56.20	$56.20
Purchase #5	$31.88	4.677%	$33.371	$33.37	$33.35	$33.40
Purchase #6	$195.26	6.768%	$208.4752	$208.48	$208.50	$208.50
Purchase #7	$59.50	5.646%	$62.8594	$62.86	$62.85	$62.90
7 purchase totals =	$813.33		$893.3209	$893.33	$893.30	$893.40