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	$223.80	5.271%	$235.5965	$235.60	$235.60	$235.60
Purchase #2	$62.86	13.865%	$71.5755	$71.58	$71.60	$71.60
Purchase #3	$65.63	3.242%	$67.7577	$67.76	$67.75	$67.80
Purchase #4	$123.51	10.748%	$136.7849	$136.78	$136.80	$136.80
Purchase #5	$80.93	11.669%	$90.3737	$90.37	$90.35	$90.40
Purchase #6	$80.54	7.753%	$86.7843	$86.78	$86.80	$86.80
Purchase #7	$95.64	8.416%	$103.6891	$103.69	$103.70	$103.70
7 purchase totals =	$732.91		$792.5617	$792.56	$792.60	$792.70