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	$47.41	12.631%	$53.3984	$53.40	$53.40	$53.40
Purchase #2	$186.81	5.124%	$196.3821	$196.38	$196.40	$196.40
Purchase #3	$152.98	5.430%	$161.2868	$161.29	$161.30	$161.30
Purchase #4	$250.79	5.108%	$263.6004	$263.60	$263.60	$263.60
Purchase #5	$18.42	10.813%	$20.4118	$20.41	$20.40	$20.40
Purchase #6	$125.81	6.553%	$134.0543	$134.05	$134.05	$134.10
Purchase #7	$181.37	5.569%	$191.4705	$191.47	$191.45	$191.50
7 purchase totals =	$963.59		$1,020.6043	$1,020.60	$1,020.60	$1,020.70