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	$109.33	4.727%	$114.498	$114.50	$114.50	$114.50
Purchase #2	$99.48	3.864%	$103.3239	$103.32	$103.30	$103.30
Purchase #3	$222.74	11.498%	$248.3506	$248.35	$248.35	$248.40
Purchase #4	$211.51	11.613%	$236.0727	$236.07	$236.05	$236.10
Purchase #5	$51.52	11.263%	$57.3227	$57.32	$57.30	$57.30
Purchase #6	$72.76	12.441%	$81.8121	$81.81	$81.80	$81.80
Purchase #7	$237.72	3.709%	$246.537	$246.54	$246.55	$246.50
7 purchase totals =	$1,005.06		$1,087.9170	$1,087.91	$1,087.85	$1,087.90