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	$162.80	10.515%	$179.9184	$179.92	$179.90	$179.90
Purchase #2	$90.40	10.348%	$99.7546	$99.75	$99.75	$99.80
Purchase #3	$71.69	3.782%	$74.4013	$74.40	$74.40	$74.40
Purchase #4	$49.61	9.819%	$54.4812	$54.48	$54.50	$54.50
Purchase #5	$239.85	10.421%	$264.8448	$264.84	$264.85	$264.80
Purchase #6	$244.52	7.103%	$261.8883	$261.89	$261.90	$261.90
Purchase #7	$104.77	11.471%	$116.7882	$116.79	$116.80	$116.80
7 purchase totals =	$963.64		$1,052.0768	$1,052.07	$1,052.10	$1,052.10