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	$73.31	11.608%	$81.8198	$81.82	$81.80	$81.80
Purchase #2	$181.51	5.165%	$190.885	$190.89	$190.90	$190.90
Purchase #3	$148.30	13.242%	$167.9379	$167.94	$167.95	$167.90
Purchase #4	$225.52	10.592%	$249.4071	$249.41	$249.40	$249.40
Purchase #5	$210.77	12.258%	$236.6062	$236.61	$236.60	$236.60
Purchase #6	$245.46	11.687%	$274.1469	$274.15	$274.15	$274.10
Purchase #7	$143.43	13.332%	$162.5521	$162.55	$162.55	$162.60
7 purchase totals =	$1,228.30		$1,363.3550	$1,363.37	$1,363.35	$1,363.30