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	$104.95	6.466%	$111.7361	$111.74	$111.75	$111.70
Purchase #2	$237.86	6.573%	$253.4945	$253.49	$253.50	$253.50
Purchase #3	$152.38	4.505%	$159.2447	$159.24	$159.25	$159.20
Purchase #4	$207.56	3.848%	$215.5469	$215.55	$215.55	$215.50
Purchase #5	$43.98	11.214%	$48.9119	$48.91	$48.90	$48.90
Purchase #6	$86.32	13.227%	$97.7375	$97.74	$97.75	$97.70
Purchase #7	$242.73	9.539%	$265.884	$265.88	$265.90	$265.90
7 purchase totals =	$1,075.78		$1,152.5556	$1,152.55	$1,152.60	$1,152.40