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	$89.60	5.836%	$94.8291	$94.83	$94.85	$94.80
Purchase #2	$166.97	12.511%	$187.8596	$187.86	$187.85	$187.90
Purchase #3	$18.91	4.454%	$19.7523	$19.75	$19.75	$19.80
Purchase #4	$36.85	12.797%	$41.5657	$41.57	$41.55	$41.60
Purchase #5	$147.83	11.413%	$164.7018	$164.70	$164.70	$164.70
Purchase #6	$185.98	5.796%	$196.7594	$196.76	$196.75	$196.80
Purchase #7	$168.84	5.871%	$178.7526	$178.75	$178.75	$178.80
7 purchase totals =	$814.98		$884.2205	$884.22	$884.20	$884.40