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	$175.81	11.623%	$196.2444	$196.24	$196.25	$196.20
Purchase #2	$218.62	11.315%	$243.3569	$243.36	$243.35	$243.40
Purchase #3	$73.71	11.457%	$82.155	$82.16	$82.15	$82.20
Purchase #4	$148.72	5.855%	$157.4276	$157.43	$157.45	$157.40
Purchase #5	$116.71	10.750%	$129.2563	$129.26	$129.25	$129.30
Purchase #6	$39.89	7.754%	$42.9831	$42.98	$43.00	$43.00
Purchase #7	$178.67	11.353%	$198.9544	$198.95	$198.95	$199.00
7 purchase totals =	$952.13		$1,050.3777	$1,050.38	$1,050.40	$1,050.50