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	$100.90	9.280%	$110.2635	$110.26	$110.25	$110.30
Purchase #2	$137.94	13.486%	$156.5426	$156.54	$156.55	$156.50
Purchase #3	$106.77	12.498%	$120.1141	$120.11	$120.10	$120.10
Purchase #4	$53.32	13.414%	$60.4723	$60.47	$60.45	$60.50
Purchase #5	$224.79	4.581%	$235.0876	$235.09	$235.10	$235.10
Purchase #6	$63.89	6.308%	$67.9202	$67.92	$67.90	$67.90
Purchase #7	$239.83	10.693%	$265.475	$265.48	$265.50	$265.50
7 purchase totals =	$927.44		$1,015.8753	$1,015.87	$1,015.85	$1,015.90