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	$183.87	3.301%	$189.9395	$189.94	$189.95	$189.90
Purchase #2	$142.40	7.767%	$153.4602	$153.46	$153.45	$153.50
Purchase #3	$159.71	9.150%	$174.3235	$174.32	$174.30	$174.30
Purchase #4	$118.59	5.813%	$125.4836	$125.48	$125.50	$125.50
Purchase #5	$184.73	6.522%	$196.7781	$196.78	$196.80	$196.80
Purchase #6	$92.59	5.701%	$97.8686	$97.87	$97.85	$97.90
Purchase #7	$189.87	8.425%	$205.8665	$205.87	$205.85	$205.90
7 purchase totals =	$1,071.76		$1,143.7200	$1,143.72	$1,143.70	$1,143.80