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	$152.72	7.636%	$164.3817	$164.38	$164.40	$164.40
Purchase #2	$118.35	7.867%	$127.6606	$127.66	$127.65	$127.70
Purchase #3	$211.87	13.524%	$240.5233	$240.52	$240.50	$240.50
Purchase #4	$76.88	7.847%	$82.9128	$82.91	$82.90	$82.90
Purchase #5	$205.97	5.243%	$216.769	$216.77	$216.75	$216.80
Purchase #6	$93.56	6.463%	$99.6068	$99.61	$99.60	$99.60
Purchase #7	$56.43	12.463%	$63.4629	$63.46	$63.45	$63.50
7 purchase totals =	$915.78		$995.3171	$995.31	$995.25	$995.40