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	$140.40	11.303%	$156.2694	$156.27	$156.25	$156.30
Purchase #2	$209.99	12.334%	$235.8902	$235.89	$235.90	$235.90
Purchase #3	$142.98	11.822%	$159.8831	$159.88	$159.90	$159.90
Purchase #4	$160.45	11.419%	$178.7718	$178.77	$178.75	$178.80
Purchase #5	$185.52	8.336%	$200.9849	$200.98	$201.00	$201.00
Purchase #6	$19.32	7.224%	$20.7157	$20.72	$20.70	$20.70
Purchase #7	$134.44	6.316%	$142.9312	$142.93	$142.95	$142.90
7 purchase totals =	$993.10		$1,095.4463	$1,095.44	$1,095.45	$1,095.50