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	$79.30	4.433%	$82.8154	$82.82	$82.80	$82.80
Purchase #2	$47.83	5.197%	$50.3157	$50.32	$50.30	$50.30
Purchase #3	$192.87	6.563%	$205.5281	$205.53	$205.55	$205.50
Purchase #4	$75.93	8.562%	$82.4311	$82.43	$82.45	$82.40
Purchase #5	$176.59	8.571%	$191.7255	$191.73	$191.75	$191.70
Purchase #6	$162.46	3.649%	$168.3882	$168.39	$168.40	$168.40
Purchase #7	$189.44	8.389%	$205.3321	$205.33	$205.35	$205.30
7 purchase totals =	$924.42		$986.5361	$986.55	$986.60	$986.40