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	$242.60	6.503%	$258.3763	$258.38	$258.40	$258.40
Purchase #2	$160.48	5.315%	$169.0095	$169.01	$169.00	$169.00
Purchase #3	$69.28	4.740%	$72.5639	$72.56	$72.55	$72.60
Purchase #4	$52.92	5.572%	$55.8687	$55.87	$55.85	$55.90
Purchase #5	$176.61	13.559%	$200.5565	$200.56	$200.55	$200.60
Purchase #6	$95.35	13.236%	$107.9705	$107.97	$107.95	$108.00
Purchase #7	$145.54	7.647%	$156.6694	$156.67	$156.65	$156.70
7 purchase totals =	$942.78		$1,021.0148	$1,021.02	$1,020.95	$1,021.20