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	$185.27	4.669%	$193.9203	$193.92	$193.90	$193.90
Purchase #2	$72.33	9.283%	$79.0444	$79.04	$79.05	$79.00
Purchase #3	$250.96	5.438%	$264.6072	$264.61	$264.60	$264.60
Purchase #4	$79.68	3.754%	$82.6712	$82.67	$82.65	$82.70
Purchase #5	$186.95	11.747%	$208.911	$208.91	$208.90	$208.90
Purchase #6	$58.80	3.793%	$61.0303	$61.03	$61.05	$61.00
Purchase #7	$179.91	9.134%	$196.343	$196.34	$196.35	$196.30
7 purchase totals =	$1,013.90		$1,086.5274	$1,086.52	$1,086.50	$1,086.40