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	$220.26	10.753%	$243.9446	$243.94	$243.95	$243.90
Purchase #2	$231.52	13.807%	$263.486	$263.49	$263.50	$263.50
Purchase #3	$183.70	12.400%	$206.4788	$206.48	$206.50	$206.50
Purchase #4	$230.81	6.517%	$245.8519	$245.85	$245.85	$245.90
Purchase #5	$29.57	13.586%	$33.5874	$33.59	$33.60	$33.60
Purchase #6	$79.49	3.242%	$82.0671	$82.07	$82.05	$82.10
Purchase #7	$25.52	9.474%	$27.9378	$27.94	$27.95	$27.90
7 purchase totals =	$1,000.87		$1,103.3536	$1,103.36	$1,103.40	$1,103.40