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	$78.47	11.159%	$87.2265	$87.23	$87.25	$87.20
Purchase #2	$68.54	4.265%	$71.4632	$71.46	$71.45	$71.50
Purchase #3	$141.38	10.649%	$156.4356	$156.44	$156.45	$156.40
Purchase #4	$99.42	10.412%	$109.7716	$109.77	$109.75	$109.80
Purchase #5	$194.81	12.580%	$219.3171	$219.32	$219.30	$219.30
Purchase #6	$156.44	3.570%	$162.0249	$162.02	$162.00	$162.00
Purchase #7	$133.64	9.836%	$146.7848	$146.78	$146.80	$146.80
7 purchase totals =	$872.70		$953.0237	$953.02	$953.00	$953.00