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	$183.95	3.585%	$190.5446	$190.54	$190.55	$190.50
Purchase #2	$195.50	3.503%	$202.3484	$202.35	$202.35	$202.30
Purchase #3	$55.59	7.542%	$59.7826	$59.78	$59.80	$59.80
Purchase #4	$96.99	6.539%	$103.3322	$103.33	$103.35	$103.30
Purchase #5	$165.77	8.814%	$180.381	$180.38	$180.40	$180.40
Purchase #6	$139.81	12.626%	$157.4624	$157.46	$157.45	$157.50
Purchase #7	$95.84	3.661%	$99.3487	$99.35	$99.35	$99.30
7 purchase totals =	$933.45		$993.1999	$993.19	$993.25	$993.10