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	$168.64	3.254%	$174.1275	$174.13	$174.15	$174.10
Purchase #2	$53.77	6.789%	$57.4204	$57.42	$57.40	$57.40
Purchase #3	$42.90	13.773%	$48.8086	$48.81	$48.80	$48.80
Purchase #4	$13.62	6.681%	$14.53	$14.53	$14.55	$14.50
Purchase #5	$96.91	4.767%	$101.5297	$101.53	$101.55	$101.50
Purchase #6	$62.72	12.366%	$70.476	$70.48	$70.50	$70.50
Purchase #7	$77.40	7.587%	$83.2723	$83.27	$83.25	$83.30
7 purchase totals =	$515.96		$550.1645	$550.17	$550.20	$550.10