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	$157.97	8.800%	$171.8714	$171.87	$171.85	$171.90
Purchase #2	$156.70	3.660%	$162.4352	$162.44	$162.45	$162.40
Purchase #3	$88.90	12.610%	$100.1103	$100.11	$100.10	$100.10
Purchase #4	$72.71	12.731%	$81.9667	$81.97	$81.95	$82.00
Purchase #5	$189.76	12.610%	$213.6887	$213.69	$213.70	$213.70
Purchase #6	$171.33	8.428%	$185.7697	$185.77	$185.75	$185.80
Purchase #7	$231.96	5.133%	$243.8665	$243.87	$243.85	$243.90
7 purchase totals =	$1,069.33		$1,159.7085	$1,159.72	$1,159.65	$1,159.80