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	$106.74	7.686%	$114.944	$114.94	$114.95	$114.90
Purchase #2	$207.41	12.365%	$233.0562	$233.06	$233.05	$233.10
Purchase #3	$181.89	13.497%	$206.4397	$206.44	$206.45	$206.40
Purchase #4	$67.55	5.825%	$71.4848	$71.48	$71.50	$71.50
Purchase #5	$82.59	12.818%	$93.1764	$93.18	$93.20	$93.20
Purchase #6	$163.51	11.852%	$182.8892	$182.89	$182.90	$182.90
Purchase #7	$141.84	4.218%	$147.8228	$147.82	$147.80	$147.80
7 purchase totals =	$951.53		$1,049.8131	$1,049.81	$1,049.85	$1,049.80