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	$214.31	6.349%	$227.9165	$227.92	$227.90	$227.90
Purchase #2	$38.53	9.512%	$42.195	$42.20	$42.20	$42.20
Purchase #3	$77.62	6.180%	$82.4169	$82.42	$82.40	$82.40
Purchase #4	$88.56	4.311%	$92.3778	$92.38	$92.40	$92.40
Purchase #5	$185.53	4.235%	$193.3872	$193.39	$193.40	$193.40
Purchase #6	$96.35	13.767%	$109.6145	$109.61	$109.60	$109.60
Purchase #7	$230.60	13.790%	$262.3997	$262.40	$262.40	$262.40
7 purchase totals =	$931.50		$1,010.3076	$1,010.32	$1,010.30	$1,010.30