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	$200.61	10.773%	$222.2217	$222.22	$222.20	$222.20
Purchase #2	$125.35	8.410%	$135.8919	$135.89	$135.90	$135.90
Purchase #3	$81.66	12.233%	$91.6495	$91.65	$91.65	$91.60
Purchase #4	$120.32	6.318%	$127.9218	$127.92	$127.90	$127.90
Purchase #5	$96.95	10.143%	$106.7836	$106.78	$106.80	$106.80
Purchase #6	$243.83	11.263%	$271.2926	$271.29	$271.30	$271.30
Purchase #7	$189.91	5.765%	$200.8583	$200.86	$200.85	$200.90
7 purchase totals =	$1,058.63		$1,156.6194	$1,156.61	$1,156.60	$1,156.60