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	$89.64	6.704%	$95.6495	$95.65	$95.65	$95.60
Purchase #2	$154.47	13.616%	$175.5026	$175.50	$175.50	$175.50
Purchase #3	$54.37	8.673%	$59.0855	$59.09	$59.10	$59.10
Purchase #4	$73.97	5.815%	$78.2714	$78.27	$78.25	$78.30
Purchase #5	$165.59	5.636%	$174.9227	$174.92	$174.90	$174.90
Purchase #6	$212.36	7.705%	$228.7223	$228.72	$228.70	$228.70
Purchase #7	$178.32	4.337%	$186.0537	$186.05	$186.05	$186.10
7 purchase totals =	$928.72		$998.2077	$998.20	$998.15	$998.20