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	$99.87	4.499%	$104.3632	$104.36	$104.35	$104.40
Purchase #2	$74.56	4.765%	$78.1128	$78.11	$78.10	$78.10
Purchase #3	$93.29	10.254%	$102.856	$102.86	$102.85	$102.90
Purchase #4	$166.76	12.502%	$187.6083	$187.61	$187.60	$187.60
Purchase #5	$105.99	12.150%	$118.8678	$118.87	$118.85	$118.90
Purchase #6	$78.42	9.255%	$85.6778	$85.68	$85.70	$85.70
Purchase #7	$167.32	4.773%	$175.3062	$175.31	$175.30	$175.30
7 purchase totals =	$786.21		$852.7921	$852.80	$852.75	$852.90