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	$226.76	13.521%	$257.4202	$257.42	$257.40	$257.40
Purchase #2	$72.61	13.376%	$82.3223	$82.32	$82.30	$82.30
Purchase #3	$82.74	9.275%	$90.4141	$90.41	$90.40	$90.40
Purchase #4	$32.55	12.624%	$36.6591	$36.66	$36.65	$36.70
Purchase #5	$139.89	11.695%	$156.2501	$156.25	$156.25	$156.30
Purchase #6	$178.53	13.790%	$203.1493	$203.15	$203.15	$203.10
Purchase #7	$209.40	6.291%	$222.5734	$222.57	$222.55	$222.60
7 purchase totals =	$942.48		$1,048.7885	$1,048.78	$1,048.70	$1,048.80