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	$220.87	12.530%	$248.545	$248.55	$248.55	$248.50
Purchase #2	$124.38	3.611%	$128.8714	$128.87	$128.85	$128.90
Purchase #3	$62.50	3.862%	$64.9138	$64.91	$64.90	$64.90
Purchase #4	$224.89	11.494%	$250.7389	$250.74	$250.75	$250.70
Purchase #5	$181.32	4.550%	$189.5701	$189.57	$189.55	$189.60
Purchase #6	$186.38	5.421%	$196.4837	$196.48	$196.50	$196.50
Purchase #7	$86.98	8.156%	$94.0741	$94.07	$94.05	$94.10
7 purchase totals =	$1,087.32		$1,173.1970	$1,173.19	$1,173.15	$1,173.20