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	$185.48	3.226%	$191.4636	$191.46	$191.45	$191.50
Purchase #2	$98.38	11.342%	$109.5383	$109.54	$109.55	$109.50
Purchase #3	$54.95	6.519%	$58.5322	$58.53	$58.55	$58.50
Purchase #4	$179.54	10.721%	$198.7885	$198.79	$198.80	$198.80
Purchase #5	$75.79	13.744%	$86.2066	$86.21	$86.20	$86.20
Purchase #6	$102.65	9.623%	$112.528	$112.53	$112.55	$112.50
Purchase #7	$39.32	9.509%	$43.0589	$43.06	$43.05	$43.10
7 purchase totals =	$736.11		$800.1161	$800.12	$800.15	$800.10