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	$142.27	3.627%	$147.4301	$147.43	$147.45	$147.40
Purchase #2	$55.96	13.199%	$63.3462	$63.35	$63.35	$63.30
Purchase #3	$160.53	8.627%	$174.3789	$174.38	$174.40	$174.40
Purchase #4	$106.71	10.869%	$118.3083	$118.31	$118.30	$118.30
Purchase #5	$172.72	10.417%	$190.7122	$190.71	$190.70	$190.70
Purchase #6	$141.53	6.532%	$150.7747	$150.77	$150.75	$150.80
Purchase #7	$195.68	7.548%	$210.4499	$210.45	$210.45	$210.40
7 purchase totals =	$975.40		$1,055.4003	$1,055.40	$1,055.40	$1,055.30