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	$48.27	8.742%	$52.4898	$52.49	$52.50	$52.50
Purchase #2	$96.64	7.135%	$103.5353	$103.54	$103.55	$103.50
Purchase #3	$174.95	8.544%	$189.8977	$189.90	$189.90	$189.90
Purchase #4	$235.33	8.513%	$255.3636	$255.36	$255.35	$255.40
Purchase #5	$203.70	6.178%	$216.2846	$216.28	$216.30	$216.30
Purchase #6	$122.81	3.751%	$127.4166	$127.42	$127.40	$127.40
Purchase #7	$38.42	7.841%	$41.4325	$41.43	$41.45	$41.40
7 purchase totals =	$920.12		$986.4201	$986.42	$986.45	$986.40