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	$233.94	13.132%	$264.661	$264.66	$264.65	$264.70
Purchase #2	$72.29	4.368%	$75.4476	$75.45	$75.45	$75.40
Purchase #3	$32.77	13.800%	$37.2923	$37.29	$37.30	$37.30
Purchase #4	$64.92	10.542%	$71.7639	$71.76	$71.75	$71.80
Purchase #5	$55.57	10.379%	$61.3376	$61.34	$61.35	$61.30
Purchase #6	$202.65	5.516%	$213.8282	$213.83	$213.85	$213.80
Purchase #7	$168.68	12.379%	$189.5609	$189.56	$189.55	$189.60
7 purchase totals =	$830.82		$913.8915	$913.89	$913.90	$913.90