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	$151.30	7.235%	$162.2466	$162.25	$162.25	$162.20
Purchase #2	$70.48	3.358%	$72.8467	$72.85	$72.85	$72.80
Purchase #3	$158.71	7.591%	$170.7577	$170.76	$170.75	$170.80
Purchase #4	$98.78	10.387%	$109.0403	$109.04	$109.05	$109.00
Purchase #5	$62.87	6.616%	$67.0295	$67.03	$67.05	$67.00
Purchase #6	$41.43	13.446%	$47.0007	$47.00	$47.00	$47.00
Purchase #7	$56.46	11.217%	$62.7931	$62.79	$62.80	$62.80
7 purchase totals =	$640.03		$691.7146	$691.72	$691.75	$691.60