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	$104.75	13.316%	$118.6985	$118.70	$118.70	$118.70
Purchase #2	$105.46	6.466%	$112.279	$112.28	$112.30	$112.30
Purchase #3	$89.51	13.779%	$101.8436	$101.84	$101.85	$101.80
Purchase #4	$102.28	7.288%	$109.7342	$109.73	$109.75	$109.70
Purchase #5	$69.41	13.152%	$78.5388	$78.54	$78.55	$78.50
Purchase #6	$97.89	4.701%	$102.4918	$102.49	$102.50	$102.50
Purchase #7	$210.39	9.831%	$231.0734	$231.07	$231.05	$231.10
7 purchase totals =	$779.69		$854.6593	$854.65	$854.70	$854.60