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	$248.98	11.426%	$277.4285	$277.43	$277.45	$277.40
Purchase #2	$18.59	11.423%	$20.7135	$20.71	$20.70	$20.70
Purchase #3	$190.46	3.374%	$196.8861	$196.89	$196.90	$196.90
Purchase #4	$153.53	5.314%	$161.6886	$161.69	$161.70	$161.70
Purchase #5	$189.93	7.531%	$204.2336	$204.23	$204.25	$204.20
Purchase #6	$22.43	3.254%	$23.1599	$23.16	$23.15	$23.20
Purchase #7	$137.83	10.454%	$152.2387	$152.24	$152.25	$152.20
7 purchase totals =	$961.75		$1,036.3489	$1,036.35	$1,036.40	$1,036.30