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	$169.98	9.381%	$185.9258	$185.93	$185.95	$185.90
Purchase #2	$195.52	5.637%	$206.5415	$206.54	$206.55	$206.50
Purchase #3	$55.96	7.783%	$60.3154	$60.32	$60.30	$60.30
Purchase #4	$45.78	12.648%	$51.5703	$51.57	$51.55	$51.60
Purchase #5	$174.32	11.705%	$194.7242	$194.72	$194.70	$194.70
Purchase #6	$55.52	9.607%	$60.8538	$60.85	$60.85	$60.90
Purchase #7	$244.60	6.253%	$259.8948	$259.89	$259.90	$259.90
7 purchase totals =	$941.68		$1,019.8258	$1,019.82	$1,019.80	$1,019.80