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	$168.98	9.799%	$185.5384	$185.54	$185.55	$185.50
Purchase #2	$185.63	3.243%	$191.65	$191.65	$191.65	$191.70
Purchase #3	$51.67	4.670%	$54.083	$54.08	$54.10	$54.10
Purchase #4	$132.55	3.112%	$136.675	$136.68	$136.70	$136.70
Purchase #5	$214.40	4.829%	$224.7534	$224.75	$224.75	$224.80
Purchase #6	$230.74	9.862%	$253.4956	$253.50	$253.50	$253.50
Purchase #7	$47.91	13.718%	$54.4823	$54.48	$54.50	$54.50
7 purchase totals =	$1,031.88		$1,100.6777	$1,100.68	$1,100.75	$1,100.80