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	$106.89	5.483%	$112.7508	$112.75	$112.75	$112.80
Purchase #2	$35.33	8.284%	$38.2567	$38.26	$38.25	$38.30
Purchase #3	$175.49	3.511%	$181.6515	$181.65	$181.65	$181.70
Purchase #4	$124.54	8.765%	$135.4559	$135.46	$135.45	$135.50
Purchase #5	$129.88	11.206%	$144.4344	$144.43	$144.45	$144.40
Purchase #6	$121.32	6.216%	$128.8613	$128.86	$128.85	$128.90
Purchase #7	$82.77	7.538%	$89.0092	$89.01	$89.00	$89.00
7 purchase totals =	$776.22		$830.4198	$830.42	$830.40	$830.60