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	$42.62	10.560%	$47.1207	$47.12	$47.10	$47.10
Purchase #2	$244.62	9.121%	$266.9318	$266.93	$266.95	$266.90
Purchase #3	$170.85	7.618%	$183.8654	$183.87	$183.85	$183.90
Purchase #4	$175.90	13.768%	$200.1179	$200.12	$200.10	$200.10
Purchase #5	$116.50	9.202%	$127.2203	$127.22	$127.20	$127.20
Purchase #6	$97.78	12.782%	$110.2782	$110.28	$110.30	$110.30
Purchase #7	$73.91	9.473%	$80.9115	$80.91	$80.90	$80.90
7 purchase totals =	$922.18		$1,016.4458	$1,016.45	$1,016.40	$1,016.40