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	$51.66	8.525%	$56.064	$56.06	$56.05	$56.10
Purchase #2	$58.72	7.472%	$63.1076	$63.11	$63.10	$63.10
Purchase #3	$98.82	6.765%	$105.5052	$105.51	$105.50	$105.50
Purchase #4	$157.45	8.626%	$171.0316	$171.03	$171.05	$171.00
Purchase #5	$227.34	5.680%	$240.2529	$240.25	$240.25	$240.30
Purchase #6	$170.66	10.300%	$188.238	$188.24	$188.25	$188.20
Purchase #7	$159.80	7.654%	$172.0311	$172.03	$172.05	$172.00
7 purchase totals =	$924.45		$996.2304	$996.23	$996.25	$996.20