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	$126.39	3.755%	$131.1359	$131.14	$131.15	$131.10
Purchase #2	$227.87	11.683%	$254.4921	$254.49	$254.50	$254.50
Purchase #3	$191.50	6.223%	$203.417	$203.42	$203.40	$203.40
Purchase #4	$73.87	13.113%	$83.5566	$83.56	$83.55	$83.60
Purchase #5	$212.87	7.377%	$228.5734	$228.57	$228.55	$228.60
Purchase #6	$103.63	5.491%	$109.3203	$109.32	$109.30	$109.30
Purchase #7	$105.72	6.330%	$112.4121	$112.41	$112.40	$112.40
7 purchase totals =	$1,041.85		$1,122.9074	$1,122.91	$1,122.85	$1,122.90